Apparatus for transmitting broadcast signal, apparatus for receiving broadcast signal, method for transmitting broadcast signal and method for receiving broadcast signal

ABSTRACT

The present invention proposes a method for transmitting a broadcast signal. The method for transmitting a broadcast signal according to the present invention proposes a system capable of supporting future broadcast services in an environment supporting future hybrid broadcasting using terrestrial broadcast networks and the Internet. In addition, the present invention proposes efficient signaling methods for both terrestrial broadcast networks and the Internet in an environment supporting future hybrid broadcasting.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Phase of PCT International ApplicationNo. PCT/KR2015/011037, filed on Oct. 20, 2015, which claims priorityunder 35 U.S.C. 119(e) to U.S. Provisional Application No. 62/066,331,filed on Oct. 20, 2014, and to U.S. Provisional Application No.62/069,257, filed on Oct. 27, 2014, all of which are hereby expresslyincorporated by reference into the present application.

TECHNICAL FIELD

The present invention relates to an apparatus for transmitting abroadcast signal, an apparatus for receiving a broadcast signal andmethods for transmitting and receiving a broadcast signal.

BACKGROUND ART

As analog broadcast signal transmission comes to an end, varioustechnologies for transmitting/receiving digital broadcast signals arebeing developed. A digital broadcast signal may include a larger amountof video/audio data than an analog broadcast signal and further includevarious types of additional data in addition to the video/audio data.

DISCLOSURE Technical Problem

That is, a digital broadcast system can provide HD (high definition)images, multichannel audio and various additional services. However,data transmission efficiency for transmission of large amounts of data,robustness of transmission/reception networks and network flexibility inconsideration of mobile reception equipment need to be improved fordigital broadcast.

Technical Solution

The present invention provides a system capable of effectivelysupporting future broadcast services in an environment supporting futurehybrid broadcasting using terrestrial broadcast networks and theInternet and related signaling methods.

Advantageous Effects

The present invention can control quality of service (QoS) with respectto services or service components by processing data on the basis ofservice characteristics, thereby providing various broadcast services.

The present invention can achieve transmission flexibility bytransmitting various broadcast services through the same radio frequency(RF) signal bandwidth.

The present invention can provide methods and apparatuses fortransmitting and receiving broadcast signals, which enable digitalbroadcast signals to be received without error even when a mobilereception device is used or even in an indoor environment.

The present invention can effectively support future broadcast servicesin an environment supporting future hybrid broadcasting usingterrestrial broadcast networks and the Internet.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a receiver protocol stack according to an embodimentof the present invention;

FIG. 2 illustrates a relation between an SLT and service layer signaling(SLS) according to an embodiment of the present invention:

FIG. 3 illustrates an SLT according to an embodiment of the presentinvention;

FIG. 4 illustrates SLS bootstrapping and a service discovery processaccording to an embodiment of the present invention;

FIG. 5 illustrates a USBD fragment for ROUTE/DASH according to anembodiment of the present invention:

FIG. 6 illustrates an S-TSID fragment for ROUTE/DASH according to anembodiment of the present invention:

FIG. 7 illustrates a USBD/USD fragment for MMT according to anembodiment of the present invention;

FIG. 8 illustrates a link layer protocol architecture according to anembodiment of the present invention;

FIG. 9 illustrates a structure of a base header of a link layer packetaccording to an embodiment of the present invention;

FIG. 10 illustrates a structure of an additional header of a link layerpacket according to an embodiment of the present invention:

FIG. 11 illustrates a structure of an additional header of a link layerpacket according to another embodiment of the present invention;

FIG. 12 illustrates a header structure of a link layer packet for anMPEG-2 TS packet and an encapsulation process thereof according to anembodiment of the present invention;

FIG. 13 illustrates an example of adaptation modes in IP headercompression according to an embodiment of the present invention(transmitting side):

FIG. 14 illustrates a link mapping table (LMT) and an RoHC-U descriptiontable according to an embodiment of the present invention;

FIG. 15 illustrates a structure of a link layer on a transmitter sideaccording to an embodiment of the present invention:

FIG. 16 illustrates a structure of a link layer on a receiver sideaccording to an embodiment of the present invention:

FIG. 17 illustrates a configuration of signaling transmission through alink layer according to an embodiment of the present invention(transmitting/receiving sides);

FIG. 18 illustrates an interface of a link layer according to anembodiment of the present invention;

FIG. 19 illustrates operation of a normal mode from among operationmodes of the link layer according to an embodiment of the presentinvention;

FIG. 20 illustrates operation of a transparent mode from among operationmodes of the link layer according to an embodiment of the presentinvention;

FIG. 21 illustrates a process of controlling operation modes of atransmitter and/or a receiver in the link layer according to anembodiment of the present invention;

FIG. 22 illustrates operations in the link layer and formats of a packettransferred to a physical layer depending on flag values according to anembodiment of the present invention:

FIG. 23 illustrates an IP overhead reduction process in atransmitter/receiver according to an embodiment of the presentinvention:

FIG. 24 illustrates RoHC profiles according to an embodiment of thepresent invention:

FIG. 25 illustrates processes of configuring and recovering an RoHCpacket stream with respect to configuration mode #1 according to anembodiment of the present invention;

FIG. 26 illustrates processes of configuring and recovering an RoHCpacket stream with respect to configuration mode #2 according to anembodiment of the present invention;

FIG. 27 illustrates processes of configuring and recovering an RoHCpacket stream with respect to configuration mode #3 according to anembodiment of the present invention;

FIG. 28 illustrates combinations of information which can be transmittedout of band according to an embodiment of the present invention;

FIG. 29 illustrates a packet transmitted through a data pipe accordingto an embodiment of the present invention;

FIG. 30 illustrates a syntax of a link layer packet structure accordingto an embodiment of the present invention:

FIG. 31 illustrates a structure of a header of a link layer packet whenIP packets are delivered to the link layer according to anotherembodiment of the present invention;

FIG. 32 illustrates a syntax of the link layer packet header structurewhen IP packets are delivered to the link layer according to anotherembodiment of the present invention;

FIG. 33 illustrates values of fields in the link layer packet headerwhen IP packets are transmitted to the link layer according to anotherembodiment of the present invention;

FIG. 34 illustrates a case in which one IP packet is included in a linklayer payload, in a link layer packet header structure when IP packetsare transmitted to the link layer, according to another embodiment ofthe present invention;

FIG. 35 illustrates a case in which multiple IP packets are concatenatedand included in link layer payloads, in a link layer packet headerstructure when IP packets are transmitted to the link layer, accordingto another embodiment of the present invention;

FIG. 36 illustrates a case in which one IP packet is segmented andincluded in link layer payloads, in a link layer packet header structurewhen IP packets are transmitted to the link layer, according to anotherembodiment of the present invention:

FIG. 37 illustrates link layer packets having segments, in a link layerpacket header structure when IP packets are transmitted to the linklayer, according to another embodiment of the present invention;

FIG. 38 illustrates a header of a link layer packet for RoHCtransmission according to an embodiment of the present invention;

FIG. 39 illustrates a syntax of the link layer packet header for RoHCtransmission according to an embodiment of the present invention:

FIG. 40 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #1 of the present invention;

FIG. 41 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #2 of the present invention;

FIG. 42 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #3 of the present invention;

FIG. 43 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #4 of the present invention;

FIG. 44 illustrates a structure of a link layer packet when signalinginformation is transmitted to the link layer according to anotherembodiment of the present invention;

FIG. 45 illustrates a syntax of the structure of the link layer packetwhen signaling information is transmitted to the link layer according toanother embodiment of the present invention;

FIG. 46 illustrates a structure of a link layer packet for framed packettransmission according to an embodiment of the present invention;

FIG. 47 illustrates a syntax of the structure of the link layer packetfor framed packet transmission according to an embodiment of the presentinvention;

FIG. 48 illustrates a syntax of a framed packet according to anembodiment of the present invention;

FIG. 49 illustrates a syntax of a fast information channel (FIC)according to an embodiment of the present invention;

FIG. 50 illustrates a broadcast system which issues an emergency alertaccording to an embodiment of the present invention;

FIG. 51 illustrates a syntax of an emergency alert table (EAT) accordingto an embodiment of the present invention;

FIG. 52 illustrates a method for identifying information related toheader compression, which is included in a payload of a link layerpacket according to an embodiment of the present invention;

FIG. 53 illustrates initialization information according to anembodiment of the present invention:

FIG. 54 illustrates configuration parameters according to an embodimentof the present invention:

FIG. 55 illustrates static chain information according to an embodimentof the present invention;

FIG. 56 illustrates dynamic chain information according to an embodimentof the present invention;

FIG. 57 illustrates a structure of a header of a link layer packetaccording to another embodiment of the present invention:

FIG. 58 illustrates a syntax of the structure of the header of a linklayer packet according to another embodiment of the present invention;

FIG. 59 illustrates a case in which one whole input packet is includedin a link layer payload in a link layer packet header structureaccording to another embodiment of the present invention;

FIG. 60 illustrates a case in which one segment of an input packet isincluded in a link layer payload in a link layer packet header structureaccording to another embodiment of the present invention;

FIG. 61 is a table showing a case in which one segment of an inputpacket is included in a link layer payload in a link layer packet headerstructure according to another embodiment of the present invention;

FIG. 62 illustrates a case in which multiple input packets areconcatenated and included in link layer payloads in a link layer packetheader structure according to another embodiment of the presentinvention;

FIG. 63 illustrates a case in which one whole input packet is includedin a link layer payload in a link layer packet header structureaccording to another embodiment of the present invention;

FIG. 64 is a table showing header lengths in a link layer packet headerstructure according to another embodiment of the present invention;

FIG. 65 illustrates a case in which one segment of an input packet isincluded in a link layer payload in a link layer packet header structureaccording to another embodiment of the present invention;

FIG. 66 illustrates a case in which one segment of an input packet isincluded in a link layer payload in a link layer packet header structureaccording to another embodiment of the present invention;

FIG. 67 illustrates a case in which one segment of an input packet isincluded in a link layer payload in a link layer packet header structureaccording to another embodiment of the present invention:

FIG. 68 illustrates a case in which one segment of an input packet isincluded in a link layer payload in a link layer packet header structureaccording to another embodiment of the present invention;

FIG. 69 illustrates a case in which multiple input packets areconcatenated and included in a link layer payload in a link layer packetheader structure according to another embodiment of the presentinvention;

FIG. 70 illustrates a case in which multiple input packets areconcatenated and included in a link layer payload in a link layer packetheader structure according to another embodiment of the presentinvention;

FIG. 71 illustrates a link layer packet structure when word based lengthindication is used in a link layer packet header structure according toanother embodiment of the present invention;

FIG. 72 is a table showing word based length indication according to thenumber of input packets in a link layer packet header structureaccording to another embodiment of the present invention;

FIG. 73 illustrates a method for transmitting a broadcast signalaccording to an embodiment of the present invention; and

FIG. 74 illustrates an apparatus for transmitting a broadcast signalaccording to an embodiment of the present invention.

BEST MODE

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. The detailed description, which will be given below withreference to the accompanying drawings, is intended to explain exemplaryembodiments of the present invention, rather than to show the onlyembodiments that can be implemented according to the present invention.The following detailed description includes specific details in order toprovide a thorough understanding of the present invention. However, itwill be apparent to those skilled in the art that the present inventionmay be practiced without such specific details.

Although the terms used in the present invention are selected fromgenerally known and used terms, some of the terms mentioned in thedescription of the present invention have been selected by the applicantat his or her discretion, the detailed meanings of which are describedin relevant parts of the description herein. Furthermore, it is requiredthat the present invention is understood, not simply by the actual termsused but by the meanings of each term lying within.

The present invention provides apparatuses and methods for transmittingand receiving broadcast signals for future broadcast services. Futurebroadcast services according to an embodiment of the present inventioninclude a terrestrial broadcast service, a mobile broadcast service, anultra high definition television (UHDTV) service, etc. The presentinvention may process broadcast signals for the future broadcastservices through non-MIMO (Multiple Input Multiple Output) or MIMOaccording to one embodiment. A non-MIMO scheme according to anembodiment of the present invention may include a MISO (Multiple InputSingle Output) scheme, a SISO (Single Input Single Output) scheme, etc.

FIG. 1 illustrates a receiver protocol stack according to an embodimentof the present invention.

Two schemes may be used in broadcast service delivery through abroadcast network.

In a first scheme, media processing units (MPUs) are transmitted usingan MMT protocol (MMTP) based on MPEG media transport (MMT). In a secondscheme, dynamic adaptive streaming over HTTP (DASH) segments may betransmitted using real time object delivery over unidirectionaltransport (ROUTE) based on MPEG DASH.

Non-timed content including NRT media, EPG data, and other files isdelivered with ROUTE. Signaling may be delivered over MMTP and/or ROUTE,while bootstrap signaling information is provided by the means of theService List Table (SLT).

In hybrid service delivery, MPEG DASH over HTTP/TCP/IP is used on thebroadband side. Media files in ISO Base Media File Format (BMFF) areused as the delivery, media encapsulation and synchronization format forboth broadcast and broadband delivery. Here, hybrid service delivery mayrefer to a case in which one or more program elements are deliveredthrough a broadband path.

Services are delivered using three functional layers. These are thephysical layer, the delivery layer and the service management layer. Thephysical layer provides the mechanism by which signaling, serviceannouncement and IP packet streams are transported over the broadcastphysical layer and/or broadband physical layer. The delivery layerprovides object and object flow transport functionality. It is enabledby the MMTP or the ROUTE protocol, operating on a UDP/IP multicast overthe broadcast physical layer, and enabled by the HTTP protocol on aTCP/IP unicast over the broadband physical layer. The service managementlayer enables any type of service, such as linear TV or HTML5application service, to be carried by the underlying delivery andphysical layers.

In this figure, a protocol stack part on a broadcast side may be dividedinto a part transmitted through the SLT and the MMTP, and a parttransmitted through ROUTE.

The SLT may be encapsulated through UDP and IP layers. Here, the SLTwill be described below. The MMTP may transmit data formatted in an MPUformat defined in MMT, and signaling information according to the MMTP.The data may be encapsulated through the UDP and IP layers. ROUTE maytransmit data formatted in a DASH segment form, signaling information,and non-timed data such as NRT data, etc. The data may be encapsulatedthrough the UDP and IP layers. According to a given embodiment, some orall processing according to the UDP and IP layers may be omitted. Here,the illustrated signaling information may be signaling informationrelated to a service.

The part transmitted through the SLT and the MMTP and the parttransmitted through ROUTE may be processed in the UDP and IP layers, andthen encapsulated again in a data link layer. The link layer will bedescribed below. Broadcast data processed in the link layer may bemulticast as a broadcast signal through processes such asencoding/interleaving, etc. in the physical layer.

In this figure, a protocol stack part on a broadband side may betransmitted through HTTP as described above. Data formatted in a DASHsegment form, signaling information. NRT information, etc. may betransmitted through HTTP. Here, the illustrated signaling informationmay be signaling information related to a service. The data may beprocessed through the TCP layer and the IP layer, and then encapsulatedinto the link layer. According to a given embodiment, some or all of theTCP, the IP, and the link layer may be omitted. Broadband data processedthereafter may be transmitted by unicast in the broadband through aprocess for transmission in the physical layer.

Service can be a collection of media components presented to the user inaggregate; components can be of multiple media types; a Service can beeither continuous or intermittent; a Service can be Real Time orNon-Real Time; Real Time Service can consist of a sequence of TVprograms.

FIG. 2 illustrates a relation between the SLT and SLS according to anembodiment of the present invention.

Service signaling provides service discovery and descriptioninformation, and comprises two functional components: Bootstrapsignaling via the Service List Table (SLT) and the Service LayerSignaling (SLS). These represent the information which is necessary todiscover and acquire user services. The SLT enables the receiver tobuild a basic service list, and bootstrap the discovery of the SLS foreach service.

The SLT can enable very rapid acquisition of basic service information.The SLS enables the receiver to discover and access services and theircontent components. Details of the SLT and SLS will be described below.

As described in the foregoing, the SLT may be transmitted throughUDP/IP. In this instance, according to a given embodiment, datacorresponding to the SLT may be delivered through the most robust schemein this transmission.

The SLT may have access information for accessing SLS delivered by theROUTE protocol. In other words, the SLT may be bootstrapped into SLSaccording to the ROUTE protocol. The SLS is signaling informationpositioned in an upper layer of ROUTE in the above-described protocolstack, and may be delivered through ROUTE/UDP/IP. The SLS may betransmitted through one of LCT sessions included in a ROUTE session. Itis possible to access a service component corresponding to a desiredservice using the SLS.

In addition, the SLT may have access information for accessing an MMTsignaling component delivered by MMTP. In other words, the SLT may bebootstrapped into SLS according to the MMTP. The SLS may be delivered byan MMTP signaling message defined in MMT. It is possible to access astreaming service component (MPU) corresponding to a desired serviceusing the SLS. As described in the foregoing, in the present invention,an NRT service component is delivered through the ROUTE protocol, andthe SLS according to the MMTP may include information for accessing theROUTE protocol. In broadband delivery, the SLS is carried overHTTP(S)/TCP/IP.

FIG. 3 illustrates an SLT according to an embodiment of the presentinvention.

First, a description will be given of a relation among respectivelogical entities of service management, delivery, and a physical layer.

Services may be signaled as being one of two basic types. First type isa linear audio/video or audio-only service that may have an app-basedenhancement. Second type is a service whose presentation and compositionis controlled by a downloaded application that is executed uponacquisition of the service. The latter can be called an “app-based”service.

The rules regarding presence of ROUTE/LCT sessions and/or MMTP sessionsfor carrying the content components of a service may be as follows.

For broadcast delivery of a linear service without app-basedenhancement, the service's content components can be carried by either(but not both): (1) one or more ROUTE/LCT sessions, or (2) one or moreMMTP sessions.

For broadcast delivery of a linear service with app-based enhancement,the service's content components can be carried by: (1) one or moreROUTE/LCT sessions, and (2) zero or more MMTP sessions.

In certain embodiments, use of both MMTP and ROUTE for streaming mediacomponents in the same service may not be allowed.

For broadcast delivery of an app-based service, the service's contentcomponents can be carried by one or more ROUTE/LCT sessions.

Each ROUTE session comprises one or more LCT sessions which carry as awhole, or in part, the content components that make up the service. Instreaming services delivery, an LCT session may carry an individualcomponent of a user service such as an audio, video or closed captionstream. Streaming media is formatted as DASH Segments.

Each MMTP session comprises one or more MMTP packet flows which carryMMT signaling messages or as a whole, or in part, the content component.An MMTP packet flow may carry MMT signaling messages or componentsformatted as MPUs.

For the delivery of NRT User Services or system metadata, an LCT sessioncarries file-based content items. These content files may consist ofcontinuous (time-based) or discrete (non-time-based) media components ofan NRT service, or metadata such as Service Signaling or ESG fragments.Delivery of system metadata such as service signaling or ESG fragmentsmay also be achieved through the signaling message mode of MMTP.

A broadcast stream is the abstraction for an RF channel, which isdefined in terms of a carrier frequency centered within a specifiedbandwidth. It is identified by the pair [geographic area, frequency]. Aphysical layer pipe (PLP) corresponds to a portion of the RF channel.Each PLP has certain modulation and coding parameters. It is identifiedby a PLP identifier (PLPID), which is unique within the broadcast streamit belongs to. Here, PLP can be referred to as DP (data pipe).

Each service is identified by two forms of service identifier: a compactform that is used in the SLT and is unique only within the broadcastarea and a globally unique form that is used in the SLS and the ESG. AROUTE session is identified by a source IP address, destination IPaddress and destination port number. An LCT session (associated with theservice component(s) it carries) is identified by a transport sessionidentifier (TSI) which is unique within the scope of the parent ROUTEsession. Properties common to the LCT sessions, and certain propertiesunique to individual LCT sessions, are given in a ROUTE signalingstructure called a service-based transport session instance description(S-TSID), which is part of the service layer signaling. Each LCT sessionis carried over a single physical layer pipe. According to a givenembodiment, one LCT session may be transmitted through a plurality ofPLPs. Different LCT sessions of a ROUTE session may or may not becontained in different physical layer pipes. Here, the ROUTE session maybe delivered through a plurality of PLPs. The properties described inthe S-TSID include the TSI value and PLPID for each LCT session,descriptors for the delivery objects/files, and application layer FECparameters.

A MMTP session is identified by destination IP address and destinationport number. An MMTP packet flow (associated with the servicecomponent(s) it carries) is identified by a packet_id which is uniquewithin the scope of the parent MMTP session. Properties common to eachMMTP packet flow, and certain properties of MMTP packet flows, are givenin the SLT. Properties for each MMTP session are given by MMT signalingmessages, which may be carried within the MMTP session. Different MMTPpacket flows of a MMTP session may or may not be contained in differentphysical layer pipes. Here, the MMTP session may be delivered through aplurality of PLPs. The properties described in the MMT signalingmessages include the packet_id value and PLPID for each MMTP packetflow. Here, the MMT signaling messages may have a form defined in MMT,or have a deformed form according to embodiments to be described below.

Hereinafter, a description will be given of low level signaling (LLS).

Signaling information which is carried in the payload of IP packets witha well-known address/port dedicated to this function is referred to aslow level signaling (LLS). The IP address and the port number may bedifferently configured depending on embodiments. In one embodiment, LLScan be transported in IP packets with address 224.0.23.60 anddestination port 4937/udp. LLS may be positioned in a portion expressedby “SLT” on the above-described protocol stack. However, according to agiven embodiment, the LLS may be transmitted through a separate physicalchannel (dedicated channel) in a signal frame without being subjected toprocessing of the UDP/IP layer.

UDP/IP packets that deliver LLS data may be formatted in a form referredto as an LLS table. A first byte of each UDP/IP packet that delivers theLLS data may correspond to a start of the LLS table. The maximum lengthof any LLS table is limited by the largest IP packet that can bedelivered from the PHY layer, 65,507 bytes.

The LLS table may include an LLS table ID field that identifies a typeof the LLS table, and an LLS table version field that identifies aversion of the LLS table. According to a value indicated by the LLStable ID field, the LLS table may include the above-described SLT or arating region table (RRT). The RRT may have information about contentadvisory rating.

Hereinafter, the SLT will be described. LLS can be signaling informationwhich supports rapid channel scans and bootstrapping of serviceacquisition by the receiver, and SLT can be a table of signalinginformation which is used to build a basic service listing and providebootstrap discovery of SLS.

The function of the SLT is similar to that of the program associationtable (PAT) in MPEG-2 Systems, and the fast information channel (FIC)found in ATSC Systems. For a receiver first encountering the broadcastemission, this is the place to start. SLT supports a rapid channel scanwhich allows a receiver to build a list of all the services it canreceive, with their channel name, channel number, etc., and SLT providesbootstrap information that allows a receiver to discover the SLS foreach service. For ROUTE/DASH-delivered services, the bootstrapinformation includes the destination IP address and destination port ofthe LCT session that carries the SLS. For MMT/MPU-delivered services,the bootstrap information includes the destination IP address anddestination port of the MMTP session carrying the SLS.

The SLT supports rapid channel scans and service acquisition byincluding the following information about each service in the broadcaststream. First, the SLT can include information necessary to allow thepresentation of a service list that is meaningful to viewers and thatcan support initial service selection via channel number or up/downselection. Second, the SLT can include information necessary to locatethe service layer signaling for each service listed. That is, the SLTmay include access information related to a location at which the SLS isdelivered.

The illustrated SLT according to the present embodiment is expressed asan XML document having an SLT root element. According to a givenembodiment, the SLT may be expressed in a binary format or an XMLdocument.

The SLT root element of the SLT illustrated in the figure may include@bsid, @sltSectionVersion. @sltSectionNumber, @totalSltSectionNumbers,@language, @capabilities, InetSigLoc and/or Service. According to agiven embodiment, the SLT root element may further include @providerId.According to a given embodiment, the SLT root element may not include@language.

The service element may include @serviceId @SLTserviceSeqNumber,@protected, @majorChannelNo, @minorChannelNo, @serviceCategory,@shortServiceName, @hidden, @slsProtocolType, BroadcastSignaling,@slsPlpId, @slsDestinationIpAddress, @slsDestinationUdpPort,@slsSourceIpAddress, @slsMajorProtocolVersion, @SlsMinorProtocolVersion,@serviceLanguage, @broadbandAccessRequired, @capabilities and/orInetSigLoc.

According to a given embodiment, an attribute or an element of the SLTmay be added/changed/deleted. Each element included in the SLT mayadditionally have a separate attribute or element, and some attribute orelements according to the present embodiment may be omitted. Here, afield which is marked with @ may correspond to an attribute, and a fieldwhich is not marked with @ may correspond to an element.

@bsid is an identifier of the whole broadcast stream. The value of BSIDmay be unique on a regional level.

@providerId can be an index of broadcaster that is using part or all ofthis broadcast stream. This is an optional attribute. When it's notpresent, it means that this broadcast stream is being used by onebroadcaster. @providerId is not illustrated in the figure.

@sltSectionVersion can be a version number of the SLT section. ThesltSectionVersion can be incremented by 1 when a change in theinformation carried within the slt occurs. When it reaches maximumvalue, it wraps around to 0.

@sltSectionNumber can be the number, counting from 1, of this section ofthe SLT. In other words, @sltSectionNumber may correspond to a sectionnumber of the SLT section. When this field is not used,@sltSectionNumber may be set to a default value of 1.

@totalSltSectionNumbers can be the total number of sections (that is,the section with the highest sltSectionNumber) of the SLT of which thissection is part. sltSectionNumber and totalSltSectionNumbers togethercan be considered to indicate “Part M of N” of one portion of the SLTwhen it is sent in fragments. In other words, when the SLT istransmitted, transmission through fragmentation may be supported. Whenthis field is not used, @totalSltSectionNumbers may be set to a defaultvalue of 1. A case in which this field is not used may correspond to acase in which the SLT is not transmitted by being fragmented.

@language can indicate primary language of the services included in thissit instance. According to a given embodiment, a value of this field mayhave be a three-character language code defined in the ISO. This fieldmay be omitted.

@capabilities can indicate required capabilities for decoding andmeaningfully presenting the content for all the services in this sitinstance.

InetSigLoc can provide a URL telling the receiver where it can acquireany requested type of data from external server(s) via broadband. Thiselement may include @urlType as a lower field. According to a value ofthe @urlType field, a type of a URL provided by InetSigLoc may beindicated. According to a given embodiment, when the @urlType field hasa value of 0, InetSigLoc may provide a URL of a signaling server. Whenthe @urlType field has a value of 1, InetSigLoc may provide a URL of anESG server. When the @urlType field has other values, the field may bereserved for future use.

The service field is an element having information about each service,and may correspond to a service entry. Service element fieldscorresponding to the number of services indicated by the SLT may bepresent. Hereinafter, a description will be given of a lowerattribute/element of the service field.

@serviceId can be an integer number that uniquely identify this servicewithin the scope of this broadcast area. According to a givenembodiment, a scope of @serviceId may be changed. @SLTserviceSeqNumbercan be an integer number that indicates the sequence number of the SLTservice information with service ID equal to the serviceId attributeabove. SLTserviceSeqNumber value can start at 0 for each service and canbe incremented by 1 every time any attribute in this service element ischanged. If no attribute values are changed compared to the previousService element with a particular value of ServiceID thenSLTserviceSeqNumber would not be incremented. The SLTserviceSeqNumberfield wraps back to 0 after reaching the maximum value.

@protected is flag information which may indicate whether one or morecomponents for significant reproduction of the service are in aprotected state. When set to “1” (true), that one or more componentsnecessary for meaningful presentation is protected. When set to “0”(false), this flag indicates that no components necessary for meaningfulpresentation of the service are protected. Default value is false.

@majorChannelNo is an integer number representing the “major” channelnumber of the service. An example of the field may have a range of 1 to999.

@minorChannelNo is an integer number representing the “minor” channelnumber of the service. An example of the field may have a range of 1 to999.

@serviceCategory can indicate the category of this service. This fieldmay indicate a type that varies depending on embodiments. According to agiven embodiment, when this field has values of 1, 2, and 3, the valuesmay correspond to a linear A/V service, a linear audio only service, andan app-based service, respectively. When this field has a value of 0,the value may correspond to a service of an undefined category. Whenthis field has other values except for 1, 2, and 3, the field may bereserved for future use. @shortServiceName can be a short string name ofthe Service.

@hidden can be boolean value that when present and set to “true”indicates that the service is intended for testing or proprietary use,and is not to be selected by ordinary TV receivers. The default value is“false” when not present.

@slsProtocolType can be an attribute indicating the type of protocol ofService Layer Signaling used by this service. This field may indicate atype that varies depending on embodiments. According to a givenembodiment, when this field has values of 1 and 2, protocols of SLS usedby respective corresponding services may be ROUTE and MMTP,respectively. When this field has other values except for 0, the fieldmay be reserved for future use. This field may be referred to as@slsProtocol.

BroadcastSignaling and lower attributes/elements thereof may provideinformation related to broadcast signaling. When the BroadcastSignalingelement is not present, the child element InetSigLoc of the parentservice element can be present and its attribute urlType includesURL_type 0x00 (URL to signaling server). In this case attribute urlsupports the query parameter svc=<service_id> where service_idcorresponds to the serviceId attribute for the parent service element.

Alternatively when the BroadcastSignaling element is not present, theelement InetSigLoc can be present as a child element of the slt rootelement and the attribute urlType of that InetSigLoc element includesURL_type 0x00 (URL to signaling server). In this case, attribute url forURL_type 0x00 supports the query parameter svc=<service_id> whereservice_id corresponds to the serviceId attribute for the parent Serviceelement.

@slsPlpId can be a string representing an integer number indicating thePLP ID of the physical layer pipe carrying the SLS for this service.

@slsDestinationIpAddress can be a string containing the dotted-IPv4destination address of the packets carrying SLS data for this service.

@slsDestinationUdpPort can be a string containing the port number of thepackets carrying SLS data for this service. As described in theforegoing, SLS bootstrapping may be performed by destination IP/UDPinformation.

@slsSourceIpAddress can be a string containing the dotted-IPv4 sourceaddress of the packets carrying SLS data for this service.

@slsMajorProtocolVersion can be major version number of the protocolused to deliver the service layer signaling for this service. Defaultvalue is 1.

@SlsMinorProtocolVersion can be minor version number of the protocolused to deliver the service layer signaling for this service. Defaultvalue is 0.

@serviceLanguage can be a three-character language code indicating theprimary language of the service. A value of this field may have a formthat varies depending on embodiments.

@broadbandAccessRequired can be a Boolean indicating that broadbandaccess is required for a receiver to make a meaningful presentation ofthe service. Default value is false. When this field has a value ofTrue, the receiver needs to access a broadband for significant servicereproduction, which may correspond to a case of hybrid service delivery.

@capabilities can represent required capabilities for decoding andmeaningfully presenting the content for the service with service IDequal to the service Id attribute above.

InetSigLoc can provide a URL for access to signaling or announcementinformation via broadband, if available. Its data type can be anextension of the any URL data type, adding an @urlType attribute thatindicates what the URL gives access to. An @urlType field of this fieldmay indicate the same meaning as that of the @urlType field ofInetSigLoc described above. When an InetSigLoc element of attributeURL_type 0x00 is present as an element of the SLT, it can be used tomake HTTP requests for signaling metadata. The HTTP POST message bodymay include a service term. When the InetSigLoc element appears at thesection level, the service term is used to indicate the service to whichthe requested signaling metadata objects apply. If the service term isnot present, then the signaling metadata objects for all services in thesection are requested. When the InetSigLoc appears at the service level,then no service term is needed to designate the desired service. When anInetSigLoc element of attribute URL_type 0x01 is provided, it can beused to retrieve ESG data via broadband. If the element appears as achild element of the service element, then the URL can be used toretrieve ESG data for that service. If the element appears as a childelement of the SLT element, then the URL can be used to retrieve ESGdata for all services in that section.

In another example of the SLT, @sltSectionVersion, @sltSectionNumber,@totalSltSectionNumbers and/or @language fields of the SLT may beomitted

In addition, the above-described InetSigLoc field may be replaced by@sltlnetSigUri and/or @sltInetEsgUri field. The two fields may includethe URI of the signaling server and URI information of the ESG server,respectively. The InetSigLoc field corresponding to a lower field of theSLT and the InetSigLoc field corresponding to a lower field of theservice field may be replaced in a similar manner.

The suggested default values may vary depending on embodiments. Anillustrated “use” column relates to the respective fields. Here, “1” mayindicate that a corresponding field is an essential field, and “0 . . .1” may indicate that a corresponding field is an optional field.

FIG. 4 illustrates SLS bootstrapping and a service discovery processaccording to an embodiment of the present invention.

Hereinafter, SLS will be described.

SLS can be signaling which provides information for discovery andacquisition of services and their content components.

For ROUTE/DASH, the SLS for each service describes characteristics ofthe service, such as a list of its components and where to acquire them,and the receiver capabilities required to make a meaningful presentationof the service. In the ROUTE/DASH system, the SLS includes the userservice bundle description (USBD), the S-TSID and the DASH mediapresentation description (MPD). Here, USBD or user service description(USD) is one of SLS XML fragments, and may function as a signaling herbthat describes specific descriptive information. USBD/USD may beextended beyond 3GPP MBMS. Details of USBD/USD will be described below.

The service signaling focuses on basic attributes of the service itself,especially those attributes needed to acquire the service. Properties ofthe service and programming that are intended for viewers appear asservice announcement, or ESG data.

Having separate Service Signaling for each service permits a receiver toacquire the appropriate SLS for a service of interest without the needto parse the entire SLS carried within a broadcast stream.

For optional broadband delivery of Service Signaling, the SLT caninclude HTTP URLs where the Service Signaling files can be obtained, asdescribed above.

LLS is used for bootstrapping SLS acquisition, and subsequently, the SLSis used to acquire service components delivered on either ROUTE sessionsor MMTP sessions. The described figure illustrates the followingsignaling sequences. Receiver starts acquiring the SLT described above.Each service identified by service_id delivered over ROUTE sessionsprovides SLS bootstrapping information: PLPID(#1), source IP address(sIP1), destination IP address (dIP1), and destination port number(dPort1). Each service identified by service_id delivered over MMTPsessions provides SLS bootstrapping information: PLPID(#2), destinationIP address (dIP2), and destination port number (dPort2).

For streaming services delivery using ROUTE, the receiver can acquireSLS fragments carried over the IP/UDP/LCT session and PLP; whereas forstreaming services delivery using MMTP, the receiver can acquire SLSfragments carried over an MMTP session and PLP. For service deliveryusing ROUTE, these SLS fragments include USBD/USD fragments, S-TSIDfragments, and MPD fragments. They are relevant to one service. USBD/USDfragments describe service layer properties and provide URI referencesto S-TSID fragments and URI references to MPD fragments. In other words,the USBD/USD may refer to S-TSID and MPD. For service delivery usingMMTP, the USBD references the MMT signaling's MPT message, the MP Tableof which provides identification of package ID and location informationfor assets belonging to the service. Here, an asset is a multimedia dataentity, and may refer to a data entity which is combined into one uniqueID and is used to generate one multimedia presentation. The asset maycorrespond to a service component included in one service. The MPTmessage is a message having the MP table of MMT. Here, the MP table maybe an MMT package table having information about content and an MMTasset. Details may be similar to a definition in MMT. Here, mediapresentation may correspond to a collection of data that establishesbounded/unbounded presentation of media content.

The S-TSID fragment provides component acquisition informationassociated with one service and mapping between DASH Representationsfound in the MPD and in the TSI corresponding to the component of theservice. The S-TSID can provide component acquisition information in theform of a TSI and the associated DASH representation identifier, andPLPID carrying DASH segments associated with the DASH representation. Bythe PLPID and TSI values, the receiver collects the audio/videocomponents from the service and begins buffering DASH media segmentsthen applies the appropriate decoding processes.

For USBD listing service components delivered on MMTP sessions, asillustrated by “Service #2” in the described figure, the receiver alsoacquires an MPT message with matching MMT_package_id to complete theSLS. An MPT message provides the full list of service componentscomprising a service and the acquisition information for each component.Component acquisition information includes MMTP session information, thePLPID carrying the session and the packet_id within that session.

According to a given embodiment, for example, in ROUTE, two or moreS-TSID fragments may be used. Each fragment may provide accessinformation related to LCT sessions delivering content of each service.

In ROUTE, S-TSID, USBD/USD, MPD, or an LCT session delivering S-TSID,USBD/USD or MPD may be referred to as a service signaling channel. InMMTP, USBD/UD, an MMT signaling message, or a packet flow delivering theMMTP or USBD/UD may be referred to as a service signaling channel.

Unlike the illustrated example, one ROUTE or MMTP session may bedelivered through a plurality of PLPs. In other words, one service maybe delivered through one or more PLPs. As described in the foregoing,one LCT session may be delivered through one PLP. Unlike the figure,according to a given embodiment, components included in one service maybe delivered through different ROUTE sessions. In addition, according toa given embodiment, components included in one service may be deliveredthrough different MMTP sessions. According to a given embodiment,components included in one service may be delivered separately through aROUTE session and an MMTP session. Although not illustrated, componentsincluded in one service may be delivered via broadband (hybriddelivery).

FIG. 5 illustrates a USBD fragment for ROUTE/DASH according to anembodiment of the present invention.

Hereinafter, a description will be given of SLS in delivery based onROUTE.

SLS provides detailed technical information to the receiver to enablethe discovery and access of services and their content components. Itcan include a set of XML-encoded metadata fragments carried over adedicated LCT session. That LCT session can be acquired using thebootstrap information contained in the SLT as described above. The SLSis defined on a per-service level, and it describes the characteristicsand access information of the service, such as a list of its contentcomponents and how to acquire them, and the receiver capabilitiesrequired to make a meaningful presentation of the service. In theROUTE/DASH system, for linear services delivery, the SLS consists of thefollowing metadata fragments: USBD, S-TSID and the DASH MPD. The SLSfragments can be delivered on a dedicated LCT transport session withTSI=0. According to a given embodiment, a TSI of a particular LCTsession (dedicated LCT session) in which an SLS fragment is deliveredmay have a different value. According to a given embodiment, an LCTsession in which an SLS fragment is delivered may be signaled using theSLT or another scheme.

ROUTE/DASH SLS can include the user service bundle description (USBD)and service-based transport session instance description (S-TSID)metadata fragments. These service signaling fragments are applicable toboth linear and application-based services. The USBD fragment containsservice identification, device capabilities information, references toother SLS fragments required to access the service and constituent mediacomponents, and metadata to enable the receiver to determine thetransport mode (broadcast and/or broadband) of service components. TheS-TSID fragment, referenced by the USBD, provides transport sessiondescriptions for the one or more ROUTE/LCT sessions in which the mediacontent components of a service are delivered, and descriptions of thedelivery objects carried in those LCT sessions. The USBD and S-TSID willbe described below.

In streaming content signaling in ROUTE-based delivery, a streamingcontent signaling component of SLS corresponds to an MPD fragment. TheMPD is typically associated with linear services for the delivery ofDASH Segments as streaming content. The MPD provides the resourceidentifiers for individual media components of the linear/streamingservice in the form of Segment URLs, and the context of the identifiedresources within the Media Presentation. Details of the MPD will bedescribed below.

In app-based enhancement signaling in ROUTE-based delivery, app-basedenhancement signaling pertains to the delivery of app-based enhancementcomponents, such as an application logic file, locally-cached mediafiles, an network content items, or a notification stream. Anapplication can also retrieve locally-cached data over a broadbandconnection when available.

Hereinafter, a description will be given of details of USBD/USDillustrated in the figure.

The top level or entry point SLS fragment is the USBD fragment. Anillustrated USBD fragment is an example of the present invention, basicfields of the USBD fragment not illustrated in the figure may beadditionally provided according to a given embodiment. As described inthe foregoing, the illustrated USBD fragment has an extended form, andmay have fields added to a basic configuration.

The illustrated USBD may have a bundleDescription root element. ThebundleDescription root element may have a userServiceDescriptionelement. The userServiceDescription element may correspond to aninstance for one service.

The userServiceDescription element may include @serviceId,@atsc:serviceId, @atsc:serviceStatus, @atsc:fullMPDUri, @atsc:sTSIDUri,name, serviceLanguage, atsc:capabilityCode and/or delivery Method.

@serviceId can be a globally unique URI that identifies a service,unique within the scope of the BSID. This parameter can be used to linkto ESG data (Service@globalServiceID).

@atsc:serviceId is a reference to corresponding service entry inLLS(SLT). The value of this attribute is the same value of serviceIdassigned to the entry.

@atsc:serviceStatus can specify the status of this service. The valueindicates whether this service is active or inactive. When set to “1”(true), that indicates service is active. When this field is not used,@atsc:serviceStatus may be set to a default value of 1.

@atsc:fullMPDUri can reference an MPD fragment which containsdescriptions for contents components of the service delivered overbroadcast and optionally. also over broadband.

@atsc:sTSIDUri can reference the S-TSID fragment which provides accessrelated parameters to the Transport sessions carrying contents of thisservice.

name can indicate name of the service as given by the lang attribute.name element can include lang attribute, which indicating language ofthe service name. The language can be specified according to XML datatypes.

serviceLanguage can represent available languages of the service. Thelanguage can be specified according to XML data types.

atsc:capabilityCode can specify the capabilities required in thereceiver to be able to create a meaningful presentation of the contentof this service. According to a given embodiment, this field may specifya predefined capability group. Here, the capability group may be a groupof capability attribute values for significant presentation. This fieldmay be omitted according to a given embodiment.

deliveyMethod can be a container of transport related informationpertaining to the contents of the service over broadcast and(optionally) broadband modes of access. Referring to data included inthe service, when the number of the data is N. delivery schemes forrespective data may be described by this element. The deliveryMethod mayinclude an r12:broadcastAppService element and an r12:unicastAppServiceelement. Each lower element may include a basePattern element as a lowerelement.

r12:broadcastAppService can be a DASH Representation delivered overbroadcast, in multiplexed or non-multiplexed form, containing thecorresponding media component(s) belonging to the service, across allPeriods of the affiliated media presentation. In other words, each ofthe fields may indicate DASH representation delivered through thebroadcast network.

r12:unicastAppService can be a DASH Representation delivered overbroadband, in multiplexed or non-multiplexed form, containing theconstituent media content component(s) belonging to the service, acrossall periods of the affiliated media presentation. In other words, eachof the fields may indicate DASH representation delivered via broadband.

basePattern can be a character pattern for use by the the receiver tomatch against any portion of the segment URL used by the DASH client torequest media segments of a parent representation under its containingperiod. A match implies that the corresponding requested media segmentis carried over broadcast transport. In a URL address for receiving DASHrepresentation expressed by each of the r12:broadcastAppService elementand the r12:unicastAppService element, a part of the URL, etc. may havea particular pattern. The pattern may be described by this field. Somedata may be distinguished using this information. The proposed defaultvalues may vary depending on embodiments. The “use” column illustratedin the figure relates to each field. Here, M may denote an essentialfield, O may denote an optional field, OD may denote an optional fieldhaving a default value, and CM may denote a conditional essential field.0 . . . 1 to 0 . . . N may indicate the number of available fields.

FIG. 6 illustrates an S-TSID fragment for ROUTE/DASH according to anembodiment of the present invention.

Hereinafter, a description will be given of the S-TSID illustrated inthe figure in detail.

S-TSID can be an SLS XML fragment which provides the overall sessiondescription information for transport session(s) which carry the contentcomponents of a service. The S-TSID is the SLS metadata fragment thatcontains the overall transport session description information for thezero or more ROUTE sessions and constituent LCT sessions in which themedia content components of a service are delivered. The S-TSID alsoincludes file metadata for the delivery object or object flow carried inthe LCT sessions of the service, as well as additional information onthe payload formats and content components carried in those LCTsessions.

Each instance of the S-TSID fragment is referenced in the USBD fragmentby the @atsc:sTSIDUri attribute of the userServiceDescription element.The illustrated S-TSID according to the present embodiment is expressedas an XML document. According to a given embodiment, the S-TSID may beexpressed in a binary format or as an XML document.

The illustrated S-TSID may have an S-TSID root element. The S-TSID rootelement may include @serviceId and/or RS.

@serviceID can be a reference corresponding service element in the USD.The value of this attribute can reference a service with a correspondingvalue of service_id.

The RS element may have information about a ROUTE session for deliveringthe service data. Service data or service components may be deliveredthrough a plurality of ROUTE sessions, and thus the number of RSelements may be 1 to N.

The RS element may include @bsid, @sIpAddr, @dIpAddr, @dport, @PLPIDand/or LS.

@bsid can be an identifier of the broadcast stream within which thecontent component(s) of the broadcastAppService are carried. When thisattribute is absent, the default broadcast stream is the one whose PLPscarry SLS fragments for this service. Its value can be identical to thatof the broadcast_stream_id in the SLT.

@sIpAddr can indicate source IP address. Here, the source IP address maybe a source IP address of a ROUTE session for delivering a servicecomponent included in the service. As described in the foregoing,service components of one service may be delivered through a pluralityof ROUTE sessions. Thus, the service components may be transmitted usinganother ROUTE session other than the ROUTE session for delivering theS-TSID. Therefore, this field may be used to indicate the source IPaddress of the ROUTE session. A default value of this field may be asource IP address of a current ROUTE session. When a service componentis delivered through another ROUTE session, and thus the ROUTE sessionneeds to be indicated, a value of this field may be a value of a sourceIP address of the ROUTE session. In this case, this field may correspondto M. that is, an essential field.

@dIpAddr can indicate destination IP address. Here, a destination IPaddress may be a destination IP address of a ROUTE session that deliversa service component included in a service. For a similar case to theabove description of @sIpAddr, this field may indicate a destination IPaddress of a ROUTE session that delivers a service component. A defaultvalue of this field may be a destination IP address of a current ROUTEsession. When a service component is delivered through another ROUTEsession, and thus the ROUTE session needs to be indicated, a value ofthis field may be a value of a destination IP address of the ROUTEsession. In this case, this field may correspond to M, that is, anessential field.

@dport can indicate destination port. Here, a destination port may be adestination port of a ROUTE session that delivers a service componentincluded in a service. For a similar case to the above description of@sIpAddr, this field may indicate a destination port of a ROUTE sessionthat delivers a service component. A default value of this field may bea destination port number of a current ROUTE session. When a servicecomponent is delivered through another ROUTE session, and thus the ROUTEsession needs to be indicated, a value of this field may be adestination port number value of the ROUTE session. In this case, thisfield may correspond to M. that is, an essential field.

@PLPID may be an ID of a PLP for a ROUTE session expressed by an RS. Adefault value may be an ID of a PLP of an LCT session including acurrent S-TSID. According to a given embodiment, this field may have anID value of a PLP for an LCT session for delivering an S-TSID in theROUTE session, and may have ID values of all PLPs for the ROUTE session.

An LS element may have information about an LCT session for delivering aservice data. Service data or service components may be deliveredthrough a plurality of LCT sessions, and thus the number of LS elementsmay be 1 to N.

The LS element may include @tsi, @PLPID, @bw, @startTime, @endTime,SrcFlow and/or RprFlow.

@tsi may indicate a TSI value of an LCT session for delivering a servicecomponent of a service.

@PLPID may have ID information of a PLP for the LCT session. This valuemay be overwritten on a basic ROUTE session value.

@bw may indicate a maximum bandwidth value. @startTime may indicate astart time of the LCT session. @endTime may indicate an end time of theLCT session. A SrcFlow element may describe a source flow of ROUTE. ARprFlow element may describe a repair flow of ROUTE.

The proposed default values may be varied according to an embodiment.The “use” column illustrated in the figure relates to each field. Here,M may denote an essential field, O may denote an optional field, OD maydenote an optional field having a default value, and CM may denote aconditional essential field. 0 . . . 1 to 0 . . . N may indicate thenumber of available fields.

Hereinafter, a description will be given of MPD for ROUTE/DASH.

The MPD is an SLS metadata fragment which contains a formalizeddescription of a DASH Media Presentation, corresponding to a linearservice of a given duration defined by the broadcaster (for example asingle TV program, or the set of contiguous linear TV programs over aperiod of time). The contents of the MPD provide the resourceidentifiers for Segments and the context for the identified resourceswithin the Media Presentation. The data structure and semantics of theMPD fragment can be according to the MPD defined by MPEG DASH.

One or more of the DASH Representations conveyed in the MPD can becarried over broadcast. The MPD may describe additional Representationsdelivered over broadband, e.g. in the case of a hybrid service, or tosupport service continuity in handoff from broadcast to broadcast due tobroadcast signal degradation (e.g. driving through a tunnel).

FIG. 7 illustrates a USBD/USD fragment for MMT according to anembodiment of the present invention.

MMT SLS for linear services comprises the USBD fragment and the MMTPackage (MP) table. The MP table is as described above. The USBDfragment contains service identification, device capabilitiesinformation, references to other SLS information required to access theservice and constituent media components, and the metadata to enable thereceiver to determine the transport mode (broadcast and/or broadband) ofthe service components. The MP table for MPU components, referenced bythe USBD, provides transport session descriptions for the MMTP sessionsin which the media content components of a service are delivered and thedescriptions of the Assets carried in those MMTP sessions.

The streaming content signaling component of the SLS for MPU componentscorresponds to the MP table defined in MMT. The MP table provides a listof MMT assets where each asset corresponds to a single service componentand the description of the location information for this component.

USBD fragments may also contain references to the S-TSID and the MPD asdescribed above, for service components delivered by the ROUTE protocoland the broadband, respectively. According to a given embodiment, indelivery through MMT, a service component delivered through the ROUTEprotocol is NRT data, etc. Thus, in this case, MPD may be unnecessary.In addition, in delivery through MMT, information about an LCT sessionfor delivering a service component, which is delivered via broadband, isunnecessary, and thus an S-TSID may be unnecessary. Here, an MMT packagemay be a logical collection of media data delivered using MMT. Here, anMMTP packet may refer to a formatted unit of media data delivered usingMMT. An MPU may refer to a generic container of independently decodabletimed/non-timed data. Here, data in the MPU is media codec agnostic.

Hereinafter, a description will be given of details of the USBD/USDillustrated in the figure.

The illustrated USBD fragment is an example of the present invention,and basic fields of the USBD fragment may be additionally providedaccording to an embodiment. As described in the foregoing, theillustrated USBD fragment has an extended form, and may have fieldsadded to a basic structure.

The illustrated USBD according to an embodiment of the present inventionis expressed as an XML document. According to a given embodiment, theUSBD may be expressed in a binary format or as an XML document.

The illustrated USBD may have a bundleDescription root element. ThebundleDescription root element may have a userServiceDescriptionelement. The userServiceDescription element may be an instance for oneservice.

The userServiceDescription element may include @serviceId,@atsc:serviceId, name, serviceLanguage, atsc:capabilityCode,atsc:Channel, atsc:mpuComponent, atsc:routeComponent,atsc:broadbandComponent and/or atsc:ComponentInfo.

Here, @serviceId, @atsc:serviceId, name, serviceLanguage, andatsc:capabilityCode may be as described above. The lang field below thename field may be as described above. atsc:capabilityCode may be omittedaccording to a given embodiment.

The userServiceDescription element may further include anatsc:contentAdvisoryRating element according to an embodiment. Thiselement may be an optional element. atsc:contentAdvisoryRating canspecify the content advisory rating. This field is not illustrated inthe figure.

atsc:Channel may have information about a channel of a service. Theatsc:Channel element may include @atsc:majorChannelNo,@atsc:minorChannelNo, @atsc:serviceLang, @atsc:serviceGenre,@atsc:serviceIcon and/or atsc:ServiceDescription. @atsc:majorChannelNo,@atsc:minorChannelNo, and @atsc:serviceLang may be omitted according toa given embodiment.

@atsc:majorChannelNo is an attribute that indicates the major channelnumber of the service.

@atsc:minorChannelNo is an attribute that indicates the minor channelnumber of the service.

@atsc:serviceLang is an attribute that indicates the primary languageused in the service.

@atsc:serviceGenre is an attribute that indicates primary genre of theservice.

@atsc:serviceIcon is an attribute that indicates the Uniform ResourceLocator (URL) for the icon used to represent this service.

atsc:ServiceDescription includes service description, possibly inmultiple languages. atsc:ServiceDescription includes can include@atsc:serviceDescrText and/or @atsc:serviceDescrLang.

@atsc:serviceDescrText is an attribute that indicates description of theservice.

@atsc:serviceDescrLang is an attribute that indicates the language ofthe serviceDescrText attribute above.

atsc:mpuComponent may have information about a content component of aservice delivered in a form of an MPU. atsc:mpuComponent may include@atsc:mmtPackageId and/or @atsc:nextMmtPackageId.

@atsc:mmtPackageId can reference a MMT Package for content components ofthe service delivered as MPUs.

@atsc:nextMmtPackageId can reference a MMT Package to be used after theone referenced by @atsc:mmtPackageId in time for content components ofthe service delivered as MPUs.

atsc:routeComponent may have information about a content component of aservice delivered through ROUTE. atsc:routeComponent may include@atsc:sTSIDUri, @sTSIDPlpId, @sTSIDDestinationIpAddress,@sTSIDDestinationUdpPort, @sTSIDSourceIpAddress,@sTSIDMajorProtocolVersion and/or @sTSIDMinorProtocolVersion.

@atsc:sTSIDUri can be a reference to the S-TSID fragment which providesaccess related parameters to the Transport sessions carrying contents ofthis service. This field may be the same as a URI for referring to anS-TSID in USBD for ROUTE described above. As described in the foregoing,in service delivery by the MMTP, service components, which are deliveredthrough NRT, etc., may be delivered by ROUTE. This field may be used torefer to the S-TSID therefor.

@sTSIDPlpId can be a string representing an integer number indicatingthe PLP ID of the physical layer pipe carrying the S-TSID for thisservice. (default: current physical layer pipe).

@sTSIDDestinationIpAddress can be a string containing the dotted-IPv4destination address of the packets carrying S-TSID for this service.(default: current MMTP session's source IP address)

@sTSIDDestinationUdpPort can be a string containing the port number ofthe packets carrying S-TSID for this service.

@sTSIDSourceIpAddress can be a string containing the dotted-IPv4 sourceaddress of the packets carrying S-TSID for this service.

@sTSIDMajorProtocolVersion can indicate major version number of theprotocol used to deliver the S-TSID for this service. Default value is1.

@sTSIDMinorProtocolVersion can indicate minor version number of theprotocol used to deliver the S-TSID for this service. Default value is0.

atsc:broadbandComponent may have information about a content componentof a service delivered via broadband. In other words,atsc:broadbandComponent may be a field on the assumption of hybriddelivery. atsc:broadbandComponent may further include @atsc:fullfMPDUri.

@atsc:fullfMPDUri can be a reference to an MPD fragment which containsdescriptions for contents components of the service delivered overbroadband.

An atsc:ComponentInfo field may have information about an availablecomponent of a service. The atsc:ComponentInfo field may haveinformation about a type, a role, a name, etc. of each component. Thenumber of atsc:ComponentInfo fields may correspond to the number (N) ofrespective components. The atsc:ComponentInfo field may include@atsc:componentType, @atsc:componentRole, @atsc:componentProtectedFlag,@atsc:componentId and/or @atsc:componentName.

@atsc:componentType is an attribute that indicates the type of thiscomponent. Value of 0 indicates an audio component. Value of 1 indicatesa video component. Value of 2 indicated a closed caption component.Value of 3 indicates an application component. Values 4 to 7 arereserved. A meaning of a value of this field may be differently setdepending on embodiments.

@atsc:componentRole is an attribute that indicates the role or kind ofthis component.

For audio (when componentType attribute above is equal to 0): values ofcomponentRole attribute are as follows: 0=Complete main, 1=Music andEffects, 2=Dialog, 3=Commentary, 4=Visually Impaired, 5=HearingImpaired, 6=Voice-Over, 7-254=reserved, 255=unknown.

For video (when componentType attribute above is equal to 1) values ofcomponentRole attribute are as follows: 0=Primary video, 1=Alternativecamera view, 2=Other alternative video component, 3=Sign language inset,4=Follow subject video, 5=3D video left view, 6=3D video right view,7=3D video depth information, 8=Part of video array <x,y> of <n,m>,9=Follow-Subject metadata, 10-254=reserved, 255=unknown.

For Closed Caption component (when componentType attribute above isequal to 2) values of componentRole attribute are as follows: 0=Normal,1=Easy reader, 2-254=reserved, 255=unknown.

When componentType attribute above is between 3 to 7, inclusive, thecomponentRole can be equal to 255. A meaning of a value of this fieldmay be differently set depending on embodiments.

@atsc:componentProtectedFlag is an attribute that indicates if thiscomponent is protected (e.g. encrypted). When this flag is set to avalue of 1 this component is protected (e.g. encrypted). When this flagis set to a value of 0 this component is not protected (e.g. encrypted).When not present the value of componentProtectedFlag attribute isinferred to be equal to 0. A meaning of a value of this field may bedifferently set depending on embodiments.

@atsc:componentId is an attribute that indicates the identifier of thiscomponent. The value of this attribute can be the same as the asset_idin the MP table corresponding to this component.

@atsc:componentName is an attribute that indicates the human readablename of this component.

The proposed default values may vary depending on embodiments. The “use”column illustrated in the figure relates to each field. Here, M maydenote an essential field, O may denote an optional field, OD may denotean optional field having a default value, and CM may denote aconditional essential field. 0 . . . 1 to 0 . . . N may indicate thenumber of available fields.

Hereinafter, a description will be given of MPD for MMT.

The Media Presentation Description is an SLS metadata fragmentcorresponding to a linear service of a given duration defined by thebroadcaster (for example a single TV program, or the set of contiguouslinear TV programs over a period of time). The contents of the MPDprovide the resource identifiers for segments and the context for theidentified resources within the media presentation. The data structureand semantics of the MPD can be according to the MPD defined by MPEGDASH.

In the present embodiment, an MPD delivered by an MMTP session describesRepresentations delivered over broadband, e.g. in the case of a hybridservice, or to support service continuity in handoff from broadcast tobroadband due to broadcast signal degradation (e.g. driving under amountain or through a tunnel).

Hereinafter, a description will be given of an MMT signaling message forMMT.

When MMTP sessions are used to carry a streaming service, MMT signalingmessages defined by MMT are delivered by MMTP packets according tosignaling message mode defined by MMT. The value of the packet_id fieldof MMTP packets carrying service layer signaling is set to ‘00’ exceptfor MMTP packets carrying MMT signaling messages specific to an asset,which can be set to the same packet_id value as the MMTP packetscarrying the asset. Identifiers referencing the appropriate package foreach service are signaled by the USBD fragment as described above. MMTPackage Table (MPT) messages with matching MMT_package_id can bedelivered on the MMTP session signaled in the SLT. Each MMTP sessioncarries MMT signaling messages specific to its session or each assetdelivered by the MMTP session.

In other words, it is possible to access USBD of the MMTP session byspecifying an IP destination address/port number, etc. of a packethaving the SLS for a particular service in the SLT. As described in theforegoing, a packet ID of an MMTP packet carrying the SLS may bedesignated as a particular value such as 00, etc. It is possible toaccess an MPT message having a matched packet ID using theabove-described package IP information of USBD. As described below, theMPT message may be used to access each service component/asset.

The following MMTP messages can be delivered by the MMTP sessionsignaled in the SLT.

MMT Package Table (MPT) message: This message carries an MP (MMTPackage) table which contains the list of all Assets and their locationinformation as defined by MMT. If an Asset is delivered by a PLPdifferent from the current PLP delivering the MP table, the identifierof the PLP carrying the asset can be provided in the MP table usingphysical layer pipe identifier descriptor. The physical layer pipeidentifier descriptor will be described below.

MMT ATSC3 (MA3) message mmt_atsc3_message( ): This message carriessystem metadata specific for services including service layer signalingas described above. mmt_atsc3_message( ) will be described below.

The following MMTP messages can be delivered by the MMTP sessionsignaled in the SLT, if required.

Media Presentation Information (MPI) message: This message carries anMPI table which contains the whole document or a subset of a document ofpresentation information. An MP table associated with the MPI table alsocan be delivered by this message.

Clock Relation Information (CRI) message: This message carries a CRItable which contains clock related information for the mapping betweenthe NTP timestamp and the MPEG-2 STC. According to a given embodiment,the CRI message may not be delivered through the MMTP session.

The following MMTP messages can be delivered by each MMTP sessioncarrying streaming content.

Hypothetical Receiver Buffer Model message: This message carriesinformation required by the receiver to manage its buffer.

Hypothetical Receiver Buffer Model Removal message: This message carriesinformation required by the receiver to manage its MMT de-capsulationbuffer.

Hereinafter, a description will be given of mmt_atsc3_message( )corresponding to one of MMT signaling messages. An MMT Signaling messagemmt_atsc3_message( ) is defined to deliver information specific toservices according to the present invention described above. Thesignaling message may include message ID, version, and/or length fieldscorresponding to basic fields of the MMT signaling message. A payload ofthe signaling message may include service ID information, content typeinformation, content version information, content compressioninformation and/or URI information. The content type information mayindicate a type of data included in the payload of the signalingmessage. The content version information may indicate a version of dataincluded in the payload, and the content compression information mayindicate a type of compression applied to the data. The URI informationmay have URI information related to content delivered by the message.

Hereinafter, a description will be given of the physical layer pipeidentifier descriptor.

The physical layer pipe identifier descriptor is a descriptor that canbe used as one of descriptors of the MP table described above. Thephysical layer pipe identifier descriptor provides information about thePLP carrying an asset. If an asset is delivered by a PLP different fromthe current PLP delivering the MP table, the physical layer pipeidentifier descriptor can be used as an asset descriptor in theassociated MP table to identify the PLP carrying the asset. The physicallayer pipe identifier descriptor may further include BSID information inaddition to PLP ID information. The BSID may be an ID of a broadcaststream that delivers an MMTP packet for an asset described by thedescriptor.

FIG. 8 illustrates a link layer protocol architecture according to anembodiment of the present invention.

Hereinafter, a link layer will be described.

The link layer is the layer between the physical layer and the networklayer, and transports the data from the network layer to the physicallayer at the sending side and transports the data from the physicallayer to the network layer at the receiving side. The purpose of thelink layer includes abstracting all input packet types into a singleformat for processing by the physical layer, ensuring flexibility andfuture extensibility for as yet undefined input types. In addition,processing within the link layer ensures that the input data can betransmitted in an efficient manner, for example by providing options tocompress redundant information in the headers of input packets. Theoperations of encapsulation, compression and so on are referred to asthe link layer protocol and packets created using this protocol arecalled link layer packets. The link layer may perform functions such aspacket encapsulation, overhead reduction and/or signaling transmission,etc.

Hereinafter, packet encapsulation will be described. Link layer protocolallows encapsulation of any type of packet, including ones such as IPpackets and MPEG-2 TS. Using link layer protocol, the physical layerneed only process one single packet format, independent of the networklayer protocol type (here we consider MPEG-2 TS packet as a kind ofnetwork layer packet.) Each network layer packet or input packet istransformed into the payload of a generic link layer packet.Additionally, concatenation and segmentation can be performed in orderto use the physical layer resources efficiently when the input packetsizes are particularly small or large.

As described in the foregoing, segmentation may be used in packetencapsulation. When the network layer packet is too large to processeasily in the physical layer, the network layer packet is divided intotwo or more segments. The link layer packet header includes protocolfields to perform segmentation on the sending side and reassembly on thereceiving side. When the network layer packet is segmented, each segmentcan be encapsulated to link layer packet in the same order as originalposition in the network layer packet. Also each link layer packet whichincludes a segment of network layer packet can be transported to PHYlayer consequently.

As described in the foregoing, concatenation may be used in packetencapsulation. When the network layer packet is small enough for thepayload of a link layer packet to include several network layer packets,the link layer packet header includes protocol fields to performconcatenation. The concatenation is combining of multiple small sizednetwork layer packets into one payload. When the network layer packetsare concatenated, each network layer packet can be concatenated topayload of link layer packet in the same order as original input order.Also each packet which constructs a payload of link layer packet can bewhole packet, not a segment of packet.

Hereinafter, overhead reduction will be described. Use of the link layerprotocol can result in significant reduction in overhead for transportof data on the physical layer. The link layer protocol according to thepresent invention may provide IP overhead reduction and/or MPEG-2 TSoverhead reduction. In IP overhead reduction, IP packets have a fixedheader format, however some of the information which is needed in acommunication environment may be redundant in a broadcast environment.Link layer protocol provides mechanisms to reduce the broadcast overheadby compressing headers of IP packets. In MPEG-2 TS overhead reduction,link layer protocol provides sync byte removal, null packet deletionand/or common header removal (compression). First, sync byte removalprovides an overhead reduction of one byte per TS packet, secondly anull packet deletion mechanism removes the 188 byte null TS packets in amanner that they can be re-inserted at the receiver and finally a commonheader removal mechanism.

For signaling transmission, in the link layer protocol, a particularformat for the signaling packet may be provided for link layersignaling, which will be described below.

In the illustrated link layer protocol architecture according to anembodiment of the present invention, link layer protocol takes as inputnetwork layer packets such as IPv4, MPEG-2 TS and so on as inputpackets. Future extension indicates other packet types and protocolwhich is also possible to be input in link layer. Link layer protocolalso specifies the format and signaling for any link layer signaling,including information about mapping to specific channel to the physicallayer. Figure also shows how ALP incorporates mechanisms to improve theefficiency of transmission, via various header compression and deletionalgorithms. In addition, the link layer protocol may basicallyencapsulate input packets.

FIG. 9 illustrates a structure of a base header of a link layer packetaccording to an embodiment of the present invention. Hereinafter, thestructure of the header will be described.

A link layer packet can include a header followed by the data payload.The header of a link layer packet can include a base header, and mayinclude an additional header depending on the control fields of the baseheader. The presence of an optional header is indicated from flag fieldsof the additional header. According to a given embodiment, a fieldindicating the presence of an additional header and an optional headermay be positioned in the base header.

Hereinafter, the structure of the base header will be described. Thebase header for link layer packet encapsulation has a hierarchicalstructure. The base header can be two bytes in length and is the minimumlength of the link layer packet header.

The illustrated base header according to the present embodiment mayinclude a Packet_Type field, a PC field and/or a length field. Accordingto a given embodiment, the base header may further include an HM fieldor an S/C field.

Packet_Type field can be a 3-bit field that indicates the originalprotocol or packet type of the input data before encapsulation into alink layer packet. An IPv4 packet, a compressed IP packet, a link layersignaling packet, and other types of packets may have the base headerstructure and may be encapsulated. However, according to a givenembodiment, the MPEG-2 TS packet may have a different particularstructure, and may be encapsulated. When the value of Packet_Type is“000”, “001” “100” or “111”, that is the original data type of an ALPpacket is one of an IPv4 packet, a compressed IP packet, link layersignaling or extension packet. When the MPEG-2 TS packet isencapsulated, the value of Packet_Type can be “010”. Other values of thePacket Type field may be reserved for future use.

Payload_Configuration (PC) field can be a 1-bit field that indicates theconfiguration of the payload. A value of 0 can indicate that the linklayer packet carries a single, whole input packet and the followingfield is the Header_Mode field. A value of 1 can indicate that the linklayer packet carries more than one input packet (concatenation) or apart of a large input packet (segmentation) and the following field isthe Segmentation_Concatenation field.

Header_Mode (HM) field can be a 1-bit field, when set to 0, that canindicate there is no additional header, and that the length of thepayload of the link layer packet is less than 2048 bytes. This value maybe varied depending on embodiments. A value of 1 can indicate that anadditional header for single packet defined below is present followingthe Length field. In this case, the length of the payload is larger than2047 bytes and/or optional features can be used (sub streamidentification, header extension, etc.). This value may be varieddepending on embodiments. This field can be present only whenPayload_Configuration field of the link layer packet has a value of 0.

Segmentation_Concatenation (S/C) field can be a 1-bit field, when set to0, that can indicate that the payload carries a segment of an inputpacket and an additional header for segmentation defined below ispresent following the Length field. A value of 1 can indicate that thepayload carries more than one complete input packet and an additionalheader for concatenation defined below is present following the Lengthfield. This field can be present only when the value ofPayload_Configuration field of the ALP packet is 1.

Length field can be a 11-bit field that indicates the 11 leastsignificant bits (LSBs) of the length in bytes of payload carried by thelink layer packet. When there is a Length_MSB field in the followingadditional header, the length field is concatenated with the Length_MSBfield, and is the LSB to provide the actual total length of the payload.The number of bits of the length field may be changed to another valuerather than 11 bits.

Following types of packet configuration are thus possible: a singlepacket without any additional header, a single packet with an additionalheader, a segmented packet and a concatenated packet. According to agiven embodiment, more packet configurations may be made through acombination of each additional header, an optional header, an additionalheader for signaling information to be described below, and anadditional header for time extension.

FIG. 10 illustrates a structure of an additional header of a link layerpacket according to an embodiment of the present invention.

Various types of additional headers may be present. Hereinafter, adescription will be given of an additional header for a single packet.

This additional header for single packet can be present when Header_Mode(HM)=“1”. The Header_Mode (HM) can be set to 1 when the length of thepayload of the link layer packet is larger than 2047 bytes or when theoptional fields are used. The additional header for single packet isshown in Figure (tsib10010).

Length_MSB field can be a 5-bit field that can indicate the mostsignificant bits (MSBs) of the total payload length in bytes in thecurrent link layer packet, and is concatenated with the Length fieldcontaining the 11 least significant bits (LSBs) to obtain the totalpayload length. The maximum length of the payload that can be signaledis therefore 65535 bytes. The number of bits of the length field may bechanged to another value rather than 11 bits. In addition, the number ofbits of the Length_MSB field may be changed, and thus a maximumexpressible payload length may be changed. According to a givenembodiment, each length field may indicate a length of a whole linklayer packet rather than a payload.

SIF (Sub stream Identifier Flag) field can be a 1-bit field that canindicate whether the sub stream ID (SID) is present after the HEF fieldor not. When there is no SID in this link layer packet, SIF field can beset to 0. When there is a SID after HEF field in the link layer packet,SIF can be set to 1. The detail of SID is described below.

HEF (Header Extension Flag) field can be a 1-bit field that canindicate, when set to 1 additional header is present for futureextension. A value of 0 can indicate that this extension header is notpresent.

Hereinafter, a description will be given of an additional header whensegmentation is used.

This additional header (tsib10020) can be present whenSegmentation_Concatenation (S/C)=“0”. Segment_Sequence_Number can be a5-bit unsigned integer that can indicate the order of the correspondingsegment carried by the link layer packet. For the link layer packetwhich carries the first segment of an input packet, the value of thisfield can be set to 0x0. This field can be incremented by one with eachadditional segment belonging to the segmented input packet.

Last_Segment_Indicator (LSI) can be a 1-bit field that can indicate,when set to 1, that the segment in this payload is the last one of inputpacket. A value of 0. can indicate that it is not last segment.

SIF (Sub stream Identifier Flag) can be a 1-bit field that can indicatewhether the SID is present after the HEF field or not. When there is noSID in the link layer packet, SIF field can be set to 0. When there is aSID after the HEF field in the link layer packet, SIF can be set to 1.

HEF (Header Extension Flag) can be a This 1-bit field that can indicate,when set to 1, that the optional header extension is present after theadditional header for future extensions of the link layer header. Avalue of 0 can indicate that optional header extension is not present.

According to a given embodiment, a packet ID field may be additionallyprovided to indicate that each segment is generated from the same inputpacket. This field may be unnecessary and thus be omitted when segmentsare transmitted in order.

Hereinafter, a description will be given of an additional header whenconcatenation is used.

This additional header (tsib10030) can be present whenSegmentation_Concatenation (S/C)=“1”.

Length_MSB can be a 4-bit field that can indicate MSB bits of thepayload length in bytes in this link layer packet. The maximum length ofthe payload is 32767 bytes for concatenation. As described in theforegoing, a specific numeric value may be changed.

Count can be a field that can indicate the number of the packetsincluded in the link layer packet. The number of the packets included inthe link layer packet, 2 can be set to this field. So, its maximum valueof concatenated packets in a link layer packet is 9. A scheme in whichthe count field indicates the number may be varied depending onembodiments. That is, the numbers from 1 to 8 may be indicated.

HEF (Header Extension Flag) can be a 1-bit field that can indicate, whenset to 1 the optional header extension is present after the additionalheader for future extensions of the link layer header. A value of 0, canindicate extension header is not present.

Component_Length can be a 12-bit length field that can indicate thelength in byte of each packet. Component_Length fields are included inthe same order as the packets present in the payload except lastcomponent packet. The number of length field can be indicated by(Count+1). According to a given embodiment, length fields, the number ofwhich is the same as a value of the count field, may be present. When alink layer header consists of an odd number of Component_Length, fourstuffing bits can follow after the last Component_Length field. Thesebits can be set to 0. According to a given embodiment, aComponent_length field indicating a length of a last concatenated inputpacket may not be present. In this case, the length of the lastconcatenated input packet may correspond to a length obtained bysubtracting a sum of values indicated by respective Component_lengthfields from a whole payload length.

Hereinafter, the optional header will be described.

As described in the foregoing, the optional header may be added to arear of the additional header. The optional header field can contain SIDand/or header extension. The SID is used to filter out specific packetstream in the link layer level. One example of SID is the role ofservice identifier in a link layer stream carrying multiple services.The mapping information between a service and the SID valuecorresponding to the service can be provided in the SLT, if applicable.The header extension contains extended field for future use. Receiverscan ignore any header extensions which they do not understand.

SID (Sub stream Identifier) can be a 8-bit field that can indicate thesub stream identifier for the link layer packet. If there is optionalheader extension, SID present between additional header and optionalheader extension.

Header_Extension ( ) can include the fields defined below.

Extension_Type can be an 8-bit field that can indicate the type of theHeader_Extension ( ).

Extension_Length can be a 8-bit field that can indicate the length ofthe Header Extension ( ) in bytes counting from the next byte to thelast byte of the Header_Extension ( ).

Extension_Byte can be a byte representing the value of theHeader_Extension ( ).

FIG. 11 illustrates a structure of an additional header of a link layerpacket according to another embodiment of the present invention.

Hereinafter, a description will be given of an additional header forsignaling information.

How link layer signaling is incorporated into link layer packets are asfollows. Signaling packets are identified by when the Packet_Type fieldof the base header is equal to 100.

Figure (tsib11010) shows the structure of the link layer packetscontaining additional header for signaling information. In addition tothe link layer header, the link layer packet can consist of twoadditional parts, additional header for signaling information and theactual signaling data itself. The total length of the link layersignaling packet is shown in the link layer packet header.

The additional header for signaling information can include followingfields. According to a given embodiment, some fields may be omitted.

Signaling_Type can be an 8-bit field that can indicate the type ofsignaling.

Signaling_Type_Extension can be a 16-bit filed that can indicate theattribute of the signaling. Detail of this field can be defined insignaling specification.

Signaling_Version can be an 8-bit field that can indicate the version ofsignaling.

Signaling_Format can be a 2-bit field that can indicate the data formatof the signaling data. Here, a signaling format may refer to a dataformat such as a binary format, an XML format, etc.

Signaling_Encoding can be a 2-bit field that can specify theencoding/compression format. This field may indicate whether compressionis not performed and which type of compression is performed.

Hereinafter, a description will be given of an additional header forpacket type extension.

In order to provide a mechanism to allow an almost unlimited number ofadditional protocol and packet types to be carried by link layer in thefuture, the additional header is defined. Packet type extension can beused when Packet_type is 111 in the base header as described above.Figure (tsib11020) shows the structure of the link layer packetscontaining additional header for type extension.

The additional header for type extension can include following fields.According to a given embodiment, some fields may be omitted.

extended_type can be a 16-bit field that can indicate the protocol orpacket type of the input encapsulated in the link layer packet aspayload. This field cannot be used for any protocol or packet typealready defined by Packet_Type field.

FIG. 12 illustrates a header structure of a link layer packet for anMPEG-2 TS packet and an encapsulation process thereof according to anembodiment of the present invention.

Hereinafter, a description will be given of a format of the link layerpacket when the MPEG-2 TS packet is input as an input packet.

In this case, the Packet_Type field of the base header is equal to 010.Multiple TS packets can be encapsulated within each link layer packet.The number of TS packets is signaled via the NUMTS field. In this case,as described in the foregoing, a particular link layer packet headerformat may be used.

Link layer provides overhead reduction mechanisms for MPEG-2 TS toenhance the transmission efficiency. The sync byte (0x47) of each TSpacket can be deleted. The option to delete NULL packets and similar TSheaders is also provided.

In order to avoid unnecessary transmission overhead, TS null packets(PID=0x1FFF) may be removed. Deleted null packets can be recovered inreceiver side using DNP field. The DNP field indicates the count ofdeleted null packets. Null packet deletion mechanism using DNP field isdescribed below.

In order to achieve more transmission efficiency, similar header ofMPEG-2 TS packets can be removed. When two or more successive TS packetshave sequentially increased continuity counter fields and other headerfields are the same, the header is sent once at the first packet and theother headers are deleted. HDM field can indicate whether the headerdeletion is performed or not. Detailed procedure of common TS headerdeletion is described below.

When all three overhead reduction mechanisms are performed, overheadreduction can be performed in sequence of sync removal, null packetdeletion, and common header deletion. According to a given embodiment, aperformance order of respective mechanisms may be changed. In addition,some mechanisms may be omitted according to a given embodiment.

The overall structure of the link layer packet header when using MPEG-2TS packet encapsulation is depicted in Figure (tsib12010).

Hereinafter, a description will be given of each illustrated field.Packet_Type can be a 3-bit field that can indicate the protocol type ofinput packet as describe above. For MPEG-2 TS packet encapsulation, thisfield can always be set to 010.

NUMTS (Number of TS packets) can be a 4-bit field that can indicate thenumber of TS packets in the payload of this link layer packet. A maximumof 16 TS packets can be supported in one link layer packet. The value ofNUMTS=0 can indicate that 16 TS packets are carried by the payload ofthe link layer packet. For all other values of NUMTS, the same number ofTS packets are recognized, e.g. NUMTS=0001 means one TS packet iscarried.

AHF (Additional Header Flag) can be a field that can indicate whetherthe additional header is present of not. A value of 0 indicates thatthere is no additional header. A value of 1 indicates that an additionalheader of length 1-byte is present following the base header. If null TSpackets are deleted or TS header compression is applied this field canbe set to 1. The additional header for TS packet encapsulation consistsof the following two fields and is present only when the value of AHF inthis link layer packet is set to 1.

HDM (Header Deletion Mode) can be a 1-bit field that indicates whetherTS header deletion can be applied to this link layer packet. A value of1 indicates that TS header deletion can be applied. A value of “0”indicates that the TS header deletion method is not applied to this linklayer packet.

DNP (Deleted Null Packets) can be a 7-bit field that indicates thenumber of deleted null TS packets prior to this link layer packet. Amaximum of 128 null TS packets can be deleted. When HDM=0 the value ofDNP=0 can indicate that 128 null packets are deleted. When HDM=1 thevalue of DNP=0 can indicate that no null packets are deleted. For allother values of DNP, the same number of null packets are recognized,e.g. DNP=5 means 5 null packets are deleted.

The number of bits of each field described above may be changed.According to the changed number of bits, a minimum/maximum value of avalue indicated by the field may be changed. These numbers may bechanged by a designer.

Hereinafter, SYNC byte removal will be described.

When encapsulating TS packets into the payload of a link layer packet,the SYNC byte (0x47) from the start of each TS packet can be deleted.Hence the length of the MPEG2-TS packet encapsulated in the payload ofthe link layer packet is always of length 187 bytes (instead of 188bytes originally).

Hereinafter, null packet deletion will be described.

Transport Stream rules require that bit rates at the output of atransmitter's multiplexer and at the input of the receiver'sde-multiplexer are constant in time and the end-to-end delay is alsoconstant. For some Transport Stream input signals, null packets may bepresent in order to accommodate variable bitrate services in a constantbitrate stream. In this case, in order to avoid unnecessary transmissionoverhead, TS null packets (that is TS packets with PID=0x1FFF) may beremoved. The process is carried-out in a way that the removed nullpackets can be re-inserted in the receiver in the exact place where theywere originally, thus guaranteeing constant bitrate and avoiding theneed for PCR time stamp updating.

Before generation of a link layer packet, a counter called DNP (DeletedNull-Packets) can first be reset to zero and then incremented for eachdeleted null packet preceding the first non-null TS packet to beencapsulated into the payload of the current link layer packet. Then agroup of consecutive useful TS packets is encapsulated into the payloadof the current link layer packet and the value of each field in itsheader can be determined. After the generated link layer packet isinjected to the physical layer, the DNP is reset to zero. When DNPreaches its maximum allowed value, if the next packet is also a nullpacket, this null packet is kept as a useful packet and encapsulatedinto the payload of the next link layer packet. Each link layer packetcan contain at least one useful TS packet in its payload.

Hereinafter, TS packet header deletion will be described. TS packetheader deletion may be referred to as TS packet header compression.

When two or more successive TS packets have sequentially increasedcontinuity counter fields and other header fields are the same, theheader is sent once at the first packet and the other headers aredeleted. When the duplicated MPEG-2 TS packets are included in two ormore successive TS packets, header deletion cannot be applied intransmitter side. HDM field can indicate whether the header deletion isperformed or not. When TS header deletion is performed, HDM can be setto 1. In the receiver side, using the first packet header, the deletedpacket headers are recovered, and the continuity counter is restored byincreasing it in order from that of the first header.

An example tsib12020 illustrated in the figure is an example of aprocess in which an input stream of a TS packet is encapsulated into alink layer packet. First, a TS stream including TS packets having SYNCbyte (0x47) may be input. First, sync bytes may be deleted through async byte deletion process. In this example, it is presumed that nullpacket deletion is not performed.

Here, it is presumed that packet headers of eight TS packets have thesame field values except for CC. that is, a continuity counter fieldvalue. In this case, TS packet deletion/compression may be performed.Seven remaining TS packet headers are deleted except for a first TSpacket header corresponding to CC=1. The processed TS packets may beencapsulated into a payload of the link layer packet.

In a completed link layer packet, a Packet_Type field corresponds to acase in which TS packets are input, and thus may have a value of 010. ANUMTS field may indicate the number of encapsulated TS packets. An AHFfield may be set to 1 to indicate the presence of an additional headersince packet header deletion is performed. An HDM field may be set to 1since header deletion is performed. DNP may be set to 0 since nullpacket deletion is not performed.

FIG. 13 illustrates an example of adaptation modes in IP headercompression according to an embodiment of the present invention(transmitting side).

Hereinafter, IP header compression will be described.

In the link layer, IP header compression/decompression scheme can beprovided. IP header compression can include two parts: headercompressor/decompressor and adaptation module. The header compressionscheme can be based on the Robust Header Compression (RoHC). Inaddition, for broadcasting usage, adaptation function is added.

In the transmitter side, ROHC compressor reduces the size of header foreach packet. Then, adaptation module extracts context information andbuilds signaling information from each packet stream. In the receiverside, adaptation module parses the signaling information associated withthe received packet stream and attaches context information to thereceived packet stream. ROHC decompressor reconstructs the original IPpacket by recovering the packet header.

The header compression scheme can be based on the RoHC as describedabove. In particular, in the present system, an RoHC framework canoperate in a unidirctional mode (U mode) of the RoHC. In addition, inthe present system, it is possible to use an RoHC UDP header compressionprofile which is identified by a profile identifier of 0x0002.

Hereinafter, adaptation will be described.

In case of transmission through the unidirectional link, if a receiverhas no information of context, decompressor cannot recover the receivedpacket header until receiving full context. This may cause channelchange delay and turn on delay. For this reason, context information andconfiguration parameters between compressor and decompressor can bealways sent with packet flow.

The Adaptation function provides out-of-band transmission of theconfiguration parameters and context information. Out-of-bandtransmission can be done through the link layer signaling. Therefore,the adaptation function is used to reduce the channel change delay anddecompression error due to loss of context information.

Hereinafter, extraction of context information will be described.

Context information may be extracted using various schemes according toadaptation mode. In the present invention, three examples will bedescribed below. The scope of the present invention is not restricted tothe examples of the adaptation mode to be described below. Here, theadaptation mode may be referred to as a context extraction mode.

Adaptation Mode 1 (not illustrated) may be a mode in which no additionaloperation is applied to a basic RoHC packet stream. In other words, theadaptation module may operate as a buffer in this mode. Therefore, inthis mode, context information may not be included in link layersignaling

In Adaptation Mode 2 (tsib13010), the adaptation module can detect theIR packet from ROHC packet flow and extract the context information(static chain). After extracting the context information, each IR packetcan be converted to an IR-DYN packet. The converted IR-DYN packet can beincluded and transmitted inside the ROHC packet flow in the same orderas IR packet, replacing the original packet.

In Adaptation Mode 3 (tsib13020), the adaptation module can detect theIR and IR-DYN packet from ROHC packet flow and extract the contextinformation. The static chain and dynamic chain can be extracted from IRpacket and dynamic chain can be extracted from IR-DYN packet. Afterextracting the context information, each IR and IR-DYN packet can beconverted to a compressed packet. The compressed packet format can bethe same with the next packet of IR or IR-DYN packet. The convertedcompressed packet can be included and transmitted inside the ROHC packetflow in the same order as IR or IR-DYN packet, replacing the originalpacket.

Signaling (context) information can be encapsulated based ontransmission structure. For example, context information can beencapsulated to the link layer signaling. In this case, the packet typevalue can be set to “100”.

In the above-described Adaptation Modes 2 and 3, a link layer packet forcontext information may have a packet type field value of 100. Inaddition, a link layer packet for compressed IP packets may have apacket type field value of 001. The values indicate that each of thesignaling information and the compressed IP packets are included in thelink layer packet as described above.

Hereinafter, a description will be given of a method of transmitting theextracted context information.

The extracted context information can be transmitted separately fromROHC packet flow, with signaling data through specific physical datapath. The transmission of context depends on the configuration of thephysical layer path. The context information can be sent with other linklayer signaling through the signaling data pipe.

In other words, the link layer packet having the context information maybe transmitted through a signaling PLP together with link layer packetshaving other link layer signaling information (Packet_Type=100).Compressed IP packets from which context information is extracted may betransmitted through a general PLP (Packet_Type=001). Here, depending onembodiments, the signaling PLP may refer to an LI signaling path. Inaddition, depending on embodiments, the signaling PLP may not beseparated from the general PLP, and may refer to a particular andgeneral PLP through which the signaling information is transmitted.

At a receiving side, prior to reception of a packet stream, a receivermay need to acquire signaling information. When receiver decodes initialPLP to acquire the signaling information, the context signaling can bealso received. After the signaling acquisition is done, the PLP toreceive packet stream can be selected. In other words, the receiver mayacquire the signaling information including the context information byselecting the initial PLP. Here, the initial PLP may be theabove-described signaling PLP. Thereafter, the receiver may select a PLPfor acquiring a packet stream. In this way, the context information maybe acquired prior to reception of the packet stream.

After the PLP for acquiring the packet stream is selected, theadaptation module can detect IR-DYN packet form received packet flow.Then, the adaptation module parses the static chain from the contextinformation in the signaling data. This is similar to receiving the IRpacket. For the same context identifier, IR-DYN packet can be recoveredto IR packet. Recovered ROHC packet flow can be sent to ROHCdecompressor. Thereafter, decompression may be started.

FIG. 14 illustrates a link mapping table (LMT) and an RoHC-U descriptiontable according to an embodiment of the present invention.

Hereinafter, link layer signaling will be described.

Generally, link layer signaling is operates under IP level. At thereceiver side, link layer signaling can be obtained earlier than IPlevel signaling such as Service List Table (SLT) and Service LayerSignaling (SLS). Therefore, link layer signaling can be obtained beforesession establishment.

For link layer signaling, there can be two kinds of signaling accordinginput path: internal link layer signaling and extemal link layersignaling. The internal link layer signaling is generated in link layerat transmitter side. And the link layer takes the signaling fromexternal module or protocol. This kind of signaling information isconsidered as external link layer signaling. If some signaling need tobe obtained prior to IP level signaling, external signaling istransmitted in format of link layer packet.

The link layer signaling can be encapsulated into link layer packet asdescribed above. The link layer packets can carn) any format of linklayer signaling, including binary and XML. The same signalinginformation may not be transmitted in different formats for the linklayer signaling.

Internal link layer signaling may include signaling information for linkmapping. The Link Mapping Table (LMT) provides a list of upper layersessions carried in a PLP. The LMT also provides addition informationfor processing the link layer packets carrying the upper layer sessionsin the link layer.

An example of the LMT (tsib14010) according to the present invention isillustrated.

signaling_type can be an 8-bit unsigned integer field that indicates thetype of signaling carried by this table. The value of signaling_typefield for Link Mapping Table (LMT) can be set to 0x01.

PLP_ID can be an 8-bit field that indicates the PLP corresponding tothis table.

num_session can be an 8-bit unsigned integer field that provides thenumber of upper layer sessions carried in the PLP identified by theabove PLP_ID field. When the value of signaling_type field is 0x01, thisfield can indicate the number of UDP/IP sessions in the PLP.

src_IP add can be a 32-bit unsigned integer field that contains thesource IP address of an upper layer session carried in the PLPidentified by the PLP_ID field.

dst_IP_add can be a 32-bit unsigned integer field that contains thedestination IP address of an upper layer session carried in the PLPidentified by the PLP_ID field.

src_UDP_port can be a 16-bit unsigned integer field that represents thesource UDP port number of an upper layer session carried in the PLPidentified by the PLP_ID field.

dst_UDP_port can be a 16-bit unsigned integer field that represents thedestination UDP port number of an upper layer session carried in the PLPidentified by the PLP_ID field.

SID_flag can be a 1-bit Boolean field that indicates whether the linklayer packet carrying the upper layer session identified by above 4fields, Src_IP_add, Dst_IP_add. Src_UDP_Port and Dst_UDP_Port, has anSID field in its optional header. When the value of this field is set to0, the link layer packet carrying the upper layer session may not havean SID field in its optional header. When the value of this field is setto 1, the link layer packet carrying the upper layer session can have anSID field in its optional header and the value the SID field can be sameas the following SID field in this table.

compressed_flag can be a 1-bit Boolean field that indicates whether theheader compression is applied the link layer packets carrying the upperlayer session identified by above 4 fields, Src_IP_add, Dst_IP_add,Src_UDP_Port and Dst_UDP_Port. When the value of this field is set to 0,the link layer packet carrying the upper layer session may have a valueof 0x00 of Packet_Type field in its base header. When the value of thisfield is set to 1, the link layer packet carrying the upper layersession may have a value of 0x01 of Packet_Type field in its base headerand the Context_ID field can be present.

SID can be an 8-bit unsigned integer field that indicates sub streamidentifier for the link layer packets carrying the upper layer sessionidentified by above 4 fields, Src_IP_add, Dst_IP_add, Src_UDP_Port andDst_UDP_Port. This field can be present when the value of SID_flag isequal to 1.

context_id can be an 8-bit field that provides a reference for thecontext id (CID) provided in the ROHC-U description table. This fieldcan be present when the value of compressed_flag is equal to 1.

An example of the RoHC-U description table (tsib14020) according to thepresent invention is illustrated. As described in the foregoing, theRoHC-U adaptation module may generate information related to headercompression.

signaling_type can be an 8-bit field that indicates the type ofsignaling carried by this table. The value of signaling_type field forROHC-U description table (RDT) can be set to “0x02”.

PLP_ID can be an 8-bit field that indicates the PLP corresponding tothis table.

context_id can be an 8-bit field that indicates the context id (CID) ofthe compressed IP stream. In this system, 8-bit CID can be used forlarge CID.

context_profile can be an 8-bit field that indicates the range ofprotocols used to compress the stream. This field can be omitted.

adaptation_mode can be a 2-bit field that indicates the mode ofadaptation module in this PLP. Adaptation modes have been describedabove.

context_config can be a 2-bit field that indicates the combination ofthe context information. If there is no context information in thistable, this field may be set to “0x0”. If the static_chain( ) ordynamic_chain( ) byte is included in this table, this field may be setto “0x01” or “0x02” respectively. If both of the static_chain( ) anddynamic_chain( ) byte are included in this table, this field may be setto “0x03”.

context_length can be an 8-bit field that indicates the length of thestatic chain byte sequence. This field can be omitted.

static_chain_byte ( ) can be a field that conveys the static informationused to initialize the ROHC-U decompressor. The size and structure ofthis field depend on the context profile.

dynamic_chain_byte ( ) can be a field that conveys the dynamicinformation used to initialize the ROHC-U decompressor. The size andstructure of this field depend on the context profile.

The static_chain_byte can be defined as sub-header information of IRpacket. The dynamic_chain_byte can be defined as sub-header informationof IR packet and IR-DYN packet.

FIG. 15 illustrates a structure of a link layer on a transmitter sideaccording to an embodiment of the present invention.

The present embodiment presumes that an IP packet is processed. From afunctional point of view, the link layer on the transmitter side maybroadly include a link layer signaling part in which signalinginformation is processed, an overhead reduction part, and/or anencapsulation part. In addition, the link layer on the transmitter sidemay include a scheduler for controlling and scheduling an overalloperation of the link layer and/or input and output parts of the linklayer.

First, signaling information of an upper layer and/or a system parametertsib15010 may be delivered to the link layer. In addition, an IP streamincluding IP packets may be delivered to the link layer from an IP layertsib15110.

As described above, the scheduler tsib15020 may determine and controloperations of several modules included in the link layer. The deliveredsignaling information and/or system parameter tsib15010 may be filtereror used by the scheduler tsib15020. Information, which corresponds to apart of the delivered signaling information and/or system parametertsib15010, necessary for a receiver may be delivered to the link layersignaling part. In addition, information, which corresponds to a part ofthe signaling information, necessary for an operation of the link layermay be delivered to an overhead reduction controller tsib15120 or anencapsulation controller tsib15180.

The link layer signaling part may collect information to be transmittedas a signal in a physical layer, and convert/configure the informationin a form suitable for transmission. The link layer signaling part mayinclude a signaling manager tsib15030, a signaling formatter tsib15040,and/or a buffer for channels tsib15050.

The signaling manager tsib15030 may receive signaling informationdelivered from the scheduler tsib15020 and/or signaling (and/or context)information delivered from the overhead reduction part. The signalingmanager tsib15030 may determine a path for transmission of the signalinginformation for delivered data. The signaling information may bedelivered through the path determined by the signaling managertsib15030. As described in the foregoing, signaling information to betransmitted through a divided channel such as the FIC, the EAS, etc. maybe delivered to the signaling formatter tsib15040, and other signalinginformation may be delivered to an encapsulation buffer tsib15070.

The signaling formatter tsib15040 may format related signalinginformation in a form suitable for each divided channel such thatsignaling information may be transmitted through a separately dividedchannel. As described in the foregoing, the physical layer may includeseparate physically/logically divided channels. The divided channels maybe used to transmit FIC signaling information or EAS-relatedinformation. The FIC or EAS-related information may be sorted by thesignaling manager tsib15030, and input to the signaling formattertsib15040. The signaling formatter tsib15040 may format the informationbased on each separate channel. When the physical layer is designed totransmit particular signaling information through a separately dividedchannel other than the FIC and the EAS, a signaling formatter for theparticular signaling information may be additionally provided. Throughthis scheme, the link layer may be compatible with various physicallayers.

The buffer for channels tsib15050 may deliver the signaling informationreceived from the signaling formatter tsib15040 to separate dedicatedchannels tsib15060. The number and content of the separate channels mayvary depending on embodiments.

As described in the foregoing, the signaling manager tsib15030 maydeliver signaling information, which is not delivered to a particularchannel, to the encapsulation buffer tsib15070. The encapsulation buffertsib15070 may function as a buffer that receives the signalinginformation which is not delivered to the particular channel.

An encapsulation block for signaling information tsib15080 mayencapsulate the signaling information which is not delivered to theparticular channel. A transmission buffer tsib15090 may function as abuffer that delivers the encapsulated signaling information to a DP forsignaling information tsib15100. Here, the DP for signaling informationtsib15100 may refer to the above-described PLS region.

The overhead reduction part may allow efficient transmission by removingoverhead of packets delivered to the link layer. It is possible toconfigure overhead reduction parts corresponding to the number of IPstreams input to the link layer.

An overhead reduction buffer tsib15130 may receive an IP packetdelivered from an upper layer. The received IP packet may be input tothe overhead reduction part through the overhead reduction buffertsib15130.

An overhead reduction controller tsib15120 may determine whether toperform overhead reduction on a packet stream input to the overheadreduction buffer tsib15130. The overhead reduction controller tsib15120may determine whether to perform overhead reduction for each packetstream. When overhead reduction is performed on a packet stream, packetsmay be delivered to a robust header compression (RoHC) compressortsib15140 to perform overhead reduction. When overhead reduction is notperformed on a packet stream, packets may be delivered to theencapsulation part to perform encapsulation without overhead reduction.Whether to perform overhead reduction of packets may be determined basedon the signaling information tsib15010 delivered to the link layer. Thesignaling information may be delivered to the encapsulation controllertsib15180 by the scheduler tsib15020.

The RoHC compressor tsib15140 may perform overhead reduction on a packetstream. The RoHC compressor tsib15140 may perform an operation ofcompressing a header of a packet. Various schemes may be used foroverhead reduction. Overhead reduction may be performed using a schemeproposed by the present invention. The present invention presumes an IPstream, and thus an expression “RoHC compressor” is used. However, thename may be changed depending on embodiments. The operation is notrestricted to compression of the IP stream, and overhead reduction ofall types of packets may be performed by the RoHC compressor tsib15140.

A packet stream configuration block tsib15150 may separate informationto be transmitted to a signaling region and information to betransmitted to a packet stream from IP packets having compressedheaders. The information to be transmitted to the packet stream mayrefer to information to be transmitted to a DP region. The informationto be transmitted to the signaling region may be delivered to asignaling and/or context controller tsib15160. The information to betransmitted to the packet stream may be transmitted to the encapsulationpart.

The signaling and/or context controller tsib15160 may collect signalingand/or context information and deliver the signaling and/or contextinformation to the signaling manager in order to transmit the signalingand/or context information to the signaling region.

The encapsulation part may perform an operation of encapsulating packetsin a form suitable for a delivery to the physical layer. It is possibleto configure encapsulation parts corresponding to the number of IPstreams.

An encapsulation buffer tsib15170 may receive a packet stream forencapsulation. Packets subjected to overhead reduction may be receivedwhen overhead reduction is performed, and an input IP packet may bereceived without change when overhead reduction is not performed.

An encapsulation controller tsib15180 may determine whether toencapsulate an input packet stream. When encapsulation is performed, thepacket stream may be delivered to a segmentation/concatenation blocktsib15190. When encapsulation is not performed, the packet stream may bedelivered to a transmission buffer tsib15230. Whether to encapsulatepackets may be determined based on the signaling information tsib15010delivered to the link layer. The signaling information may be deliveredto the encapsulation controller tsib15180 by the scheduler tsib15020.

In the segmentation/concatenation block tsib15190, the above-describedsegmentation or concatenation operation may be performed on packets. Inother words, when an input IP packet is longer than a link layer packetcorresponding to an output of the link layer, one IP packet may besegmented into several segments to configure a plurality of link layerpacket payloads. On the other hand, when an input IP packet is shorterthan a link layer packet corresponding to an output of the link layer,several IP packets may be concatenated to configure one link layerpacket payload.

A packet configuration table tsib15200 may have configurationinformation of a segmented and/or concatenated link layer packet. Atransmitter and a receiver may have the same information in the packetconfiguration table tsib15200. The transmitter and the receiver mayrefer to the information of the packet configuration table tsib15200. Anindex value of the information of the packet configuration tabletsib15200 may be included in a header of the link layer packet.

A link layer header information block tsib15210 may collect headerinformation generated in an encapsulation process. In addition, the linklayer header information block tsib15210 may collect header informationincluded in the packet configuration table tsib15200. The link layerheader information block tsib15210 may configure header informationaccording to a header structure of the link layer packet.

A header attachment block tsib15220 may add a header to a payload of asegmented and/or concatenated link layer packet. The transmission buffertsib15230 may function as a buffer to deliver the link layer packet to aDP tsib15240 of the physical layer.

The respective blocks, modules, or parts may be configured as onemodule/protocol or a plurality of modules/protocols in the link layer.

FIG. 16 illustrates a structure of a link layer on a receiver sideaccording to an embodiment of the present invention.

The present embodiment presumes that an IP packet is processed. From afunctional point of view, the link layer on the receiver side maybroadly include a link layer signaling part in which signalinginformation is processed, an overhead processing part, and/or adecapsulation part. In addition, the link layer on the receiver side mayinclude a scheduler for controlling and scheduling overall operation ofthe link layer and/or input and output parts of the link layer.

First, information received through a physical layer may be delivered tothe link layer. The link layer may process the information, restore anoriginal state before being processed at a transmitter side, and thendeliver the information to an upper layer. In the present embodiment,the upper layer may be an IP layer.

Information, which is separated in the physical layer and deliveredthrough a particular channel tsib16030, may be delivered to a link layersignaling part. The link layer signaling part may determine signalinginformation received from the physical layer, and deliver the determinedsignaling information to each part of the link layer.

A buffer for channels tsib16040 may function as a buffer that receivessignaling information transmitted through particular channels. Asdescribed in the foregoing, when physically/logically divided separatechannels are present in the physical layer, it is possible to receivesignaling information transmitted through the channels. When theinformation received from the separate channels is segmented, thesegmented information may be stored until complete information isconfigured.

A signaling decoder/parser tsib16050 may verify a format of thesignaling information received through the particular channel, andextract information to be used in the link layer. When the signalinginformation received through the particular channel is encoded, decodingmay be performed. In addition, according to a given embodiment, it ispossible to verify integrity, etc. of the signaling information.

A signaling manager tsib16060 may integrate signaling informationreceived through several paths. Signaling information received through aDP for signaling tsib16070 to be described below may be integrated inthe signaling manager tsib16060. The signaling manager tsib16060 maydeliver signaling information necessary for each part in the link layer.For example, the signaling manager tsib16060 may deliver contextinformation, etc. for recovery of a packet to the overhead processingpart. In addition, the signaling manager tsib16060 may deliver signalinginformation for control to a scheduler tsib16020.

General signaling information, which is not received through a separateparticular channel, may be received through the DP for signalingtsib16070. Here, the DP for signaling may refer to PLS, L1, etc. Here,the DP may be referred to as a PLP. A reception buffer tsib16080 mayfunction as a buffer that receives signaling information delivered fromthe DP for signaling. In a decapsulation block for signaling informationtsib16090, the received signaling information may be decapsulated. Thedecapsulated signaling information may be delivered to the signalingmanager tsib16060 through a decapsulation buffer tsib16100. As describedin the foregoing, the signaling manager tsib16060 may collate signalinginformation, and deliver the collated signaling information to anecessary part in the link layer.

The scheduler tsib16020 may determine and control operations of severalmodules included in the link layer. The scheduler tsib16020 may controleach part of the link layer using receiver information tsib16010 and/orinformation delivered from the signaling manager tsib16060. In addition,the scheduler tsib16020 may determine an operation mode, etc. of eachpart. Here, the receiver information tsib16010 may refer to informationpreviously stored in the receiver. The scheduler tsib16020 may useinformation changed by a user such as channel switching, etc. to performa control operation.

The decapsulation part may filter a packet received from a DP tsib16110of the physical layer, and separate a packet according to a type of thepacket. It is possible to configure decapsulation parts corresponding tothe number of DPs that can be simultaneously decoded in the physicallayer.

The decapsulation buffer tsib16100 may function as a buffer thatreceives a packet stream from the physical layer to performdecapsulation. A decapsulation controller tsib16130 may determinewhether to decapsulate an input packet stream. When decapsulation isperformed, the packet stream may be delivered to a link layer headerparser tsib16140. When decapsulation is not performed, the packet streammay be delivered to an output buffer tsib16220. The signalinginformation received from the scheduler tsib16020 may be used todetermine whether to perform decapsulation.

The link layer header parser tsib16140 may identify a header of thedelivered link layer packet. It is possible to identify a configurationof an IP packet included in a payload of the link layer packet byidentifying the header. For example, the IP packet may be segmented orconcatenated.

A packet configuration table tsib16150 may include payload informationof segmented and/or concatenated link layer packets. The transmitter andthe receiver may have the same information in the packet configurationtable tsib16150. The transmitter and the receiver may refer to theinformation of the packet configuration table tsib16150. It is possibleto find a value necessary for reassembly based on index informationincluded in the link layer packet.

A reassembly block tsib16160 may configure payloads of the segmentedand/or concatenated link layer packets as packets of an original IPstream. Segments may be collected and reconfigured as one IP packet, orconcatenated packets may be separated and reconfigured as a plurality ofIP packet streams. Recombined IP packets may be delivered to theoverhead processing part.

The overhead processing part may perform an operation of restoring apacket subjected to overhead reduction to an original packet as areverse operation of overhead reduction performed in the transmitter.This operation may be referred to as overhead processing. It is possibleto configure overhead processing parts corresponding to the number ofDPs that can be simultaneously decoded in the physical layer.

A packet recovery buffer tsib16170 may function as a buffer thatreceives a decapsulated RoHC packet or IP packet to perform overheadprocessing.

An overhead controller tsib16180 may determine whether to recover and/ordecompress the decapsulated packet. When recovery and/or decompressionare performed, the packet may be delivered to a packet stream recoveryblock tsib16190. When recovery and/or decompression are not performed,the packet may be delivered to the output buffer tsib16220. Whether toperform recovery and/or decompression may be determined based on thesignaling information delivered by the scheduler tsib16020.

The packet stream recovery block tsib16190 may perform an operation ofintegrating a packet stream separated from the transmitter with contextinformation of the packet stream. This operation may be a process ofrestoring a packet stream such that an RoHC decompressor tsib16210 canperform processing. In this process, it is possible to receive signalinginformation and/or context information from a signaling and/or contextcontroller tsib16200. The signaling and/or context controller tsib16200may determine signaling information delivered from the transmitter, anddeliver the signaling information to the packet stream recovery blocktsib16190 such that the signaling information may be mapped to a streamcorresponding to a context ID.

The RoHC decompressor tsib16210 may restore headers of packets of thepacket stream. The packets of the packet stream may be restored to formsof original IP packets through restoration of the headers. In otherwords, the RoHC decompressor tsib16210 may perform overhead processing.

The output buffer tsib16220 may function as a buffer before an outputstream is delivered to an IP layer tsib16230.

The link layers of the transmitter and the receiver proposed in thepresent invention may include the blocks or modules described above. Inthis way, the link layer may independently operate irrespective of anupper layer and a lower layer, overhead reduction may be efficientlyperformed, and a supportable function according to an upper/lower layermay be easily defined/added/deleted.

FIG. 17 illustrates a configuration of signaling transmission through alink layer according to an embodiment of the present invention(transmitting/receiving sides).

In the present invention, a plurality of service providers(broadcasters) may provide services within one frequency band. Inaddition, a service provider may provide a plurality of services, andone service may include one or more components. It can be consideredthat the user receives content using a service as a unit.

The present invention presumes that a transmission protocol based on aplurality of sessions is used to support an IP hybrid broadcast.Signaling information delivered through a signaling path may bedetermined based on a transmission configuration of each protocol.Various names may be applied to respective protocols according to agiven embodiment.

In the illustrated data configuration tsib17010 on the transmittingside, service providers (broadcasters) may provide a plurality ofservices (Service #1, #2, . . . ). In general, a signal for a servicemay be transmitted through a general transmission session (signaling C).However, the signal may be transmitted through a particular session(dedicated session) according to a given embodiment (signaling B).

Service data and service signaling information may be encapsulatedaccording to a transmission protocol. According to a given embodiment,an IP/UDP layer may be used. According to a given embodiment, a signalin the IP/UDP layer (signaling A) may be additionally provided. Thissignaling may be omitted.

Data processed using the IP/UDP may be input to the link layer. Asdescribed in the foregoing, overhead reduction and/or encapsulation maybe performed in the link layer. Here, link layer signaling may beadditionally provided. Link layer signaling may include a systemparameter, etc. Link layer signaling has been described above.

The service data and the signaling information subjected to the aboveprocess may be processed through PLPs in a physical layer. Here, a PLPmay be referred to as a DP. The example illustrated in the figurepresumes a case in which a base DP/PLP is used. However, depending onembodiments, transmission may be performed using only a general DP/PLPwithout the base DP/PLP.

In the example illustrated in the figure, a particular channel(dedicated channel) such as an FIC, an EAC, etc. is used. A signaldelivered through the FIC may be referred to as a fast information table(FIT), and a signal delivered through the EAC may be referred to as anemergency alert table (EAT). The FIT may be identical to theabove-described SLT. The particular channels may not be used dependingon embodiments. When the particular channel (dedicated channel) is notconfigured, the FIT and the EAT may be transmitted using a general linklayer signaling transmission scheme, or transmitted using a PLP via theIP/UDP as other service data.

According to a given embodiment, system parameters may include atransmitter-related parameter, a service provider-related parameter,etc. Link layer signaling may include IP header compression-relatedcontext information and/or identification information of data to whichthe context is applied. Signaling of an upper layer may include an IPaddress, a UDP number, service/component information, emergencyalert-related information, an IP/UDP address for service signaling, asession ID, etc. Detailed examples thereof have been described above.

In the illustrated data configuration tsib17020 on the receiving side,the receiver may decode only a PLP for a corresponding service usingsignaling information without having to decode all PLPs.

First, when the user selects or changes a service desired to bereceived, the receiver may be tuned to a corresponding frequency and mayread receiver information related to a corresponding channel stored in aDB, etc. The information stored in the DB, etc. of the receiver may beconfigured by reading an SLT at the time of initial channel scan.

After receiving the SLT and the information about the correspondingchannel, information previously stored in the DB is updated, andinformation about a transmission path of the service selected by theuser and information about a path, through which component informationis acquired or a signal necessary to acquire the information istransmitted, are acquired. When the information is not determined to bechanged using version information of the SLT, decoding or parsing may beomitted.

The receiver may verify whether SLT information is included in a PLP byparsing physical signaling of the PLP in a corresponding broadcaststream (not illustrated), which may be indicated through a particularfield of physical signaling. It is possible to access a position atwhich a service layer signal of a particular service is transmitted byaccessing the SLT information. The service layer signal may beencapsulated into the IP/UDP and delivered through a transmissionsession. It is possible to acquire information about a componentincluded in the service using this service layer signaling. A specificSLT-SLS configuration is as described above.

In other words, it is possible to acquire transmission path information,for receiving upper layer signaling information (service signalinginformation) necessary to receive the service, corresponding to one ofseveral packet streams and PLPs currently transmitted on a channel usingthe SLT. The transmission path information may include an IP address, aUDP port number, a session ID, a PLP ID, etc. Here, depending onembodiments, a value previously designated by the IANA or a system maybe used as an IP/UDP address. The information may be acquired using ascheme of accessing a DB or a shared memory, etc.

When the link layer signal and service data are transmitted through thesame PLP, or only one PLP is operated, service data delivered throughthe PLP may be temporarily stored in a device such as a buffer, etc.while the link layer signal is decoded.

It is possible to acquire information about a path through which theservice is actually transmitted using service signaling information of aservice to be received. In addition, a received packet stream may besubjected to decapsulation and header recovery using information such asoverhead reduction for a PLP to be received, etc.

In the illustrated example (tsib17020), the FIC and the EAC are used,and a concept of the base DP/PLP is presumed. As described in theforegoing, concepts of the FIC, the EAC, and the base DP/PLP may not beused.

FIG. 18 illustrates an interface of a link layer according to anembodiment of the present invention.

The figure shows a case in which a transmitter uses an IP packet and/oran MPEG2-TS packet used in digital broadcast as an input signal. Thetransmitter may support a packet structure in a new protocol which canbe used in future broadcast systems. Encapsulated data and/or signalinginformation of the link layer may be transmitted to a physical layer.The transmitter may process transmitted data (which can includesignaling data) according to a protocol of the physical layer, which issupported by a broadcast system, and transmit a signal including thedata.

A receiver restores the data and/or the signaling information receivedfrom the physical layer to data that can be processed in an upper layer.The receiver can read packet headers and determine whether packetsreceived from the physical layer include signaling information (orsignaling data) or general data (or content data).

The signaling information (i.e., signaling data) transmitted from thetransmitter may include first signaling information which is receivedfrom an upper layer and needs to be transmitted to an upper layer of thereceiver, second signaling information which is generated in the linklayer and provides information related to data processing in the linklayer of the receiver and/or third signaling information which isgenerated in the upper layer or the link layer and transmitted torapidly identify specific data (e.g. service, content and/or signalingdata) in the physical layer.

According to an embodiment of the present invention, additionalprocessing may be performed on packets, delivered from the upper layer,in the link layer.

When a packet delivered from the upper layer is an IP packet, thetransmitter can perform IP header compression in the link layer.Overhead can be reduced in IP flow through IP header compression. For IPheader compression, robust header compression (RoHC) may be used. Referto RFC3095 and RFC5795 for details of RoHC.

In one embodiment of the present invention, RoHC can operate in aunidirectional mode. This will be described in detail later.

When the packet delivered from the upper layer is an MPEG-2 transportstream (ST) packet, overhead reduction may be performed on the MPEG-2 TSpacket. The MPEG-2 TS packet may include a sync field, a null packetand/or a common packet identifier (PID). Since such data is repeated ineach TS packet or unnecessary data, the transmitter can delete the datain the link layer, generate information used for the receiver to restorethe data and transmit the information to the receiver.

The transmitter can encapsulate the packet, transmitted from the upperlayer, in the link layer. For example, the transmitter can generate alink layer packet by encapsulating the IP packet, the MPEG-2 TS packetand/or a packet in a different protocol in the link layer. Packets inone format can be processed in the physical layer of thetransmitter/receiver through encapsulation in the link layerirrespective of protocol type of the network layer. In this case, theMPEG-2 TS packet can be considered to be a packet of the network layer.

The network layer is an upper layer of the link layer. A packet of thenetwork layer can be converted into a payload of a packet of the linklayer. In an embodiment of the present invention, packets of the networklayer can be included in packets of the link layer by being concatenatedand segmented in order to efficiently use resources of the physicallayer.

When the size of packets of the network layer is small such that apayload of the link layer can include a plurality of packets of thenetwork layer, a packet header of the link layer can include a protocolfield for performing concatenation. Concatenation can be defined ascombination of a plurality of packets of the network layer in a payload(a packet payload of the link layer).

When the size of one packet of the network layer is too large to beprocessed in the physical layer, a packet of the network layer may besegmented into two or more segments. A packet header of the link layermay include necessary information in the form of a protocol field suchthat the transmitting side can segment the packet of the network layerand the receiving side can reassemble the segmented packets.

Processing of the link layer in the transmitter includes transmission ofsignaling information generated in the link layer, such as a fastinformation channel (FIC), an emergency alert system (EAS) messageand/or information for overhead reduction.

The FIC is a signaling structure including information necessary forchannel scan and fast service acquisition. That is, a main purpose ofthe FIC is to efficiently transfer information necessary for fastchannel scan and service acquisition. Information included in the FICmay correspond to information for connecting a data pipe (DP) (or PLP)and a broadcast service.

Processing of the link layer in the transmitter includes transmission ofan emergency alert message and signaling information related theretothrough a specific channel. The specific channel may correspond to achannel predefined in the physical layer. The specific channel may becalled an emergency alert channel (EAC).

FIG. 19 illustrates operation of a normal mode from among operationmodes of a link layer according to an embodiment of the presentinvention.

The link layer proposed by the present invention may have variousoperation modes for compatibility between an upper layer and a lowerlayer. The present invention proposes the normal mode and a transparentmode of the link layer. The two operation modes can coexist in the linklayer and which mode will be used can be designated using a signaling orsystem parameter. According to an embodiment, only one of the two modesmay be implemented. Different modes may be applied according to an IPlayer and a TS layer input to the link layer. Otherwise, different modesmay be applied for streams of the IP layer and streams of the TS layer.

According to an embodiment, a new operation mode may be added to thelink layer. The new operation mode may be added on the basis ofconfigurations of an upper layer and a lower layer. The new operationmode may include different interfaces on the basis of the configurationsof the upper layer and the lower layer. Whether to use the new operationmode may be designated using a signaling or system parameter.

In the normal mode, data is processed according to functions supportedby the link layer and then delivered to the physical layer.

First, packets may be respectively transferred from an IP layer, anMPEG-2 TS layer and a specific protocol layer t89010 to the link layer.That is, an IP packet can be delivered from the IP layer to the linklayer. An MPEG-2 TS packet can be delivered from the MPEG-2 TS layer tothe link layer. A specific packet can be delivered from the specificprotocol layer to the link layer.

The delivered packets may or may not be overhead-reduced t89020 and thenencapsulated t89030.

Specifically, the IP packet may or may not be overhead-reduced t89020and then encapsulated t89030. Whether overhead reduction is performedmay be designated by a signaling or system parameter. According to anembodiment, overhead reduction may or may not be performed per IPstream. The encapsulated IP packet can be delivered to the physicallayer.

The MPEG-2 TS packet may be overhead-reduced t89020 and thenencapsulated t89030. In the case of the MPEG-2 TS packet, overheadreduction may be omitted according to an embodiment. However, since ageneral TS packet has a sync byte (0x47) at the head thereof, it may beefficient to remove such fixed overhead. The encapsulated TS packet canbe delivered to the physical layer.

A packet other than the IP or TS packet may or may not beoverhead-reduced t89020 and then encapsulated t89030. Whether overheadreduction is performed may be determined according to characteristics ofthe packet. Whether overhead reduction is performed may be designated bythe signaling or system parameter. The encapsulated packet can bedelivered to the physical layer.

During overhead reduction t89020, the sizes of the input packets may bereduced through an appropriate method. During the overhead reductionprocess, specific information may be extracted or generated from theinput packets. The specific information is information related tosignaling and may be transmitted through a signaling region. Thesignaling information enables the receiver to restore the packetschanged during overhead reduction to the original packets. The signalinginformation can be delivered through link layer signaling t89050.

Link layer signaling t89050 can transmit and manage the signalinginformation extracted/generated during overhead reduction. The physicallayer may have physically/logically separated transmission paths. Linklayer signaling t89050 may deliver the signaling information to thephysical layer according to the separated transmission paths. Theseparated transmission paths may include FIC signaling t89060 and EASsignaling t89070. Signaling information which is not transmitted throughthe transmission paths may be delivered to the physical layer afterbeing subjected to encapsulation t89030.

Signaling information managed through link layer signaling t89050 mayinclude signaling information delivered from an upper layer, signalinginformation generated in the link layer and/or system parameters.Specifically, signaling information managed through link layer signalingt89050 may include signaling information that is delivered from theupper layer and needs to be transmitted to an upper layer of thereceiver, signaling information that is generated in the link layer andneeds to be used in the link layer of the receiver and signalinginformation that is generated in the upper layer or the link layer andused for fast detection in the physical layer of the receiver.

Data encapsulated t89030 and delivered to the physical layer may betransmitted through a data pipe (DP) 89040. Here, the DP may be aphysical layer pipe (PLP). Signaling information transmitted through theaforementioned separate transmission paths may be delivered torespective transmission paths. For example, FIC signaling informationcan be transmitted through an FIC channel t89080 designated in aphysical frame and EAS signaling information can be transmitted throughan EAS channel t89090 designed in the physical frame. Informationrepresenting presence of a specific channel such as an FIC or EAC can besignaled and transmitted through a preamble region of the physical frameor signaled by scrambling a preamble using a specific scramblingsequence. According to an embodiment, FIC signaling/EAS signalinginformation may be transmitted through a normal DP region, a PLS regionor a preamble instead of a designated specific channel.

The receiver can receive data and signaling information through thephysical layer. The receiver can restore the data and signalinginformation to forms that can be processed in an upper layer andtransfer the same to the upper layer. This process can be performed inthe link layer of the receiver. The receiver can determine whetherreceived packets are related to the signaling information or the data byreading headers of the packets, for example. When overhead reduction hasbeen performed at the transmitting side, the receiver can restorepackets having reduced overhead through overhead reduction to theoriginal packets. In this process, the received signaling informationcan be used.

FIG. 20 illustrates operation of the transparent mode from among theoperation modes of the link layer according to an embodiment of thepresent invention.

In the transparent mode, data can be delivered to the physical layerwithout being processed according to functions supported by the linklayer or processed according to only some of the functions and thendelivered to the physical layer. That is, packets delivered from anupper layer can be sent to the physical layer without passing throughoverhead reduction and/or encapsulation in the transparent mode. Otherpackets may be pass through overhead reduction and/or encapsulation inthe transparent mode as necessary. The transparent mode may be called abypass mode.

According to an embodiment, some packets can be processed in the normalmode and some packets can be processed in the transparent mode on thebasis of characteristics of packets and system operation.

Packets to which the transparent mode is applicable may be packets oftypes well known to the system. When the corresponding packets can beprocessed in the physical layer, the transparent mode can be used. Forexample, in the case of a known TS or IP packet, the packet can passthrough overhead reduction and input formatting processes in thephysical layer and thus the transparent mode can be used in the linklayer stage. When the transparent mode is applied and the packet isprocess through input formatting in the physical layer, theaforementioned operation such as TS header compression can be performedin the physical layer. When a normal mode is applied, a processed linklayer packet can be processed by being handled as a GS packet in thephysical layer.

Even in the transparent mode, a link layer signaling module may beprovided when it is necessary to support transmission of signalinginformation. The link layer signaling module can transmit and managesignaling information, as described above. Singling information can beencapsulated and transmitted through a DP and FIC and EAS signalinginformation having separated transmission paths can be respectivelytransmitted through an FIC channel and an EAC channel.

In the transparent mode, whether information corresponds to signalinginformation can be indicated through a method of using a fixed IPaddress and port number, for example. In this case, the signalinginformation may be filtered to configure a link layer packet and thenthe link layer packet may be transmitted through the physical layer.

FIG. 21 illustrates a process of controlling operation modes of thetransmitter and/or the receiver in the link layer according to anembodiment of the present invention.

Determination of a link layer operation mode of the transmitter or thereceiver can enable more efficient use of a broadcast system andflexible design of the broadcast system. According to the method ofcontrolling link layer modes, proposed by the present invention, linklayer modes for efficient operation of a system bandwidth and processingtime can be dynamically switched. In addition, when a specific modeneeds to be supported or need for a specific mode disappears due tochange of the physical layer, this can be easily handled. Furthermore,when a broadcaster providing broadcast services intends to designate amethod for transmitting the broadcast services, broadcast systems caneasily accept requests of the broadcaster.

The method for controlling link layer operation modes may be implementedsuch that the method is performed only in the link layer or may beperformed through data structure change in the link layer. In this case,independent operations of the network layer and/or the physical layercan be performed without additionally implementing additional functionstherein. It is possible to control link layer modes proposed by thepresent invention with signaling or system internal parameters withoutmodifying the system to adapt to the structure of the physical layer. Aspecific mode may operate only when processing of corresponding input issupported in the physical layer.

The figure shows a flow through which the transmitter/receiver processessignals and/or data in the IP layer, link layer and physical layer.

A functional block (which can be implemented as hardware and/orsoftware) for mode control may be added to the link layer to manageparameters and/or signaling information for determining whether toprocess a packet. The link layer can determine whether to execute acorresponding function in a packet stream processing procedure usinginformation stored in the mode control functional block.

Operation of the transmitted will now be described first.

When an IP stream is input to the link layer, the transmitter determineswhether to perform overhead reduction j16020 using mode controlparameters j16005 (j16010). The mode control parameters can be generatedin the transmitter by a service provider. The mode control parameterswill be described in detail later.

When overhead reduction j16020 is performed, information about overheadreduction is generated and included in link layer signaling informationj16060. The link layer signaling information j16060 may include all orsome mode control parameters. The link layer signaling informationj16060 may be delivered in the form of a link layer signaling packet.While the link layer signaling packet can be mapped to a DP anddelivered to the receiver, the link layer signaling packet may betransmitted to the receiver through a predetermined region of abroadcast signal without being mapped to a DP.

The packet stream that has passed through overhead reduction j16020 isencapsulated j16030 and applied to a DP of the physical layer (J16040).When the packet stream has not passed through overhead reduction, thetransmitter determines whether to perform encapsulation j16050 on thepacket stream.

The packet stream that has passed through encapsulation j16030 isapplied to the DP of the physical layer (j16040). Here, operation forgeneral packet (link layer packet) processing is performed in thephysical layer. When the IP stream has not passed through overheadreduction and encapsulation, the IP stream is directly delivered to thephysical layer. Then, operation for processing the IP stream isperformed in the physical layer. When the IP stream is directlytransmitted to the physical layer, parameters can be provided such thatoperation is performed only when the physical layer supports IP packetinput. That is, mode control parameter values can be controlled suchthat operation of directly transmitting an IP packet to the physicallayer is not performed when the physical layer does not support IPpacket processing.

The transmitter transmits the broadcast signal that has passed throughthe aforementioned process to the receiver.

Operation of the receiver will now be described.

When a specific DP is selected according to channel change by a user anda packet stream is received through the DP in the receiver (j16110), thereceiver can check a mode in which the corresponding packet has beengenerated when transmitted using the header of the packet stream and/orsignaling information (S16120). When the mode is confirmed for the DP,the corresponding IP packet is transmitted to the upper layer throughdecapsulation j16130 and overhead reduction j16140 in the link layer.Overhead reduction j16140 may include overhead recovery.

FIG. 22 illustrates operation in the link layer and format of a packettransmitted to the physical layer on the basis of flag values accordingto an embodiment of the present invention.

To determine an operation mode of the link layer, the aforementionedsignaling method can be used. Signaling information related to themethod can be directly transmitted to the receiver. In this case, theaforementioned signaling data or link layer signaling packet may includemode control related information which will be described later.

There may be a method of indirectly signaling an operation mode of thelink layer to the receiver in consideration of complexity of thereceiver.

The following two flags can be considered for operation mode control.

-   -   Header compression flag (HCF): this is a flag setting whether to        apply header compression in the link layer and can be assigned        values indicating “enable” and “disable”.    -   Encapsulation flag (EF): this is a flag setting whether to apply        encapsulation in the link layer and can be assigned values        indicating “enable” and “disable”. However, the EF can be        subordinated to the HCF when encapsulation needs to be        essentially performed according to header compression scheme.

A value mapped to each flag can be provided in the range includingrepresentation of “enable” and “disable” according to systemconfiguration and the number of bits allocated per flag can be changed.For example, the value “enable” can be mapped to 1 and the value“disable” can be mapped to 0.

The figure shows whether header compression and encapsulation areperformed and a packet format transferred to the physical layeraccording to header compression and encapsulation on the basis of HCFand EF values. That is, according to one embodiment of the presentinvention, the receiver can recognize the format of a packet input tothe physical layer from information about the HCF and the EF.

FIG. 23 illustrates an IP overhead reduction process in thetransmitter/receiver according to an embodiment of the presentinvention.

According to an embodiment of the present invention, when an IP streamenters the overhead reduction process, an RoHC compressor L5010 canperform header compression on the IP stream. RoHC can be used as aheader compression algorithm in an embodiment of the present invention.The packet stream that has passed through RoHC can be reconfiguredaccording to an RoHC packet format in a packet stream configurationprocess L5020, and the reconfigured RoHC packet stream can be deliveredto an encapsulation layer L5040 and then transmitted to the receiverthrough the physical layer. RoHC context information and/or signalinginformation generated during packet stream reconfiguration can be madeinto data in a transmittable form through a signaling generator L5030and the data can be delivered to an encapsulation layer or signalingmodule S5050 according to transmission form.

According to an embodiment of the present invention, the receiver canreceive a stream with respect to service data and a signaling channel orsignaling data transmitted through a separate DP. A signaling parserL5060 can receive the signaling data, parses the signaling data intoRoHC context information and/or signaling information and transmit theparsed information to a packet stream recovery unit L5070. The receivercan recover the packet stream reconfigured in the transmitter in aformat that can be decompressed by an RoHC decompressor L5080 using theRoHC context information and/or the signaling information included inthe signaling data, through the packet stream recovery unit L5070. TheRoHC decompressor L5080 can convert the recovered RoHC packet streaminto an IP stream, and the IP stream can be delivered to an upper layerthrough the IP layer.

FIG. 24 illustrates RoHC profiles according to an embodiment of thepresent invention.

According to an embodiment of the present invention, RoHC can be usedfor header compression for an upper packet in the link layer, asdescribed above. An RoHC framework can operate in the unidirectionalmode, as described in RFC 3095, in consideration of characteristics ofbroadcast networks. The RoHC framework defines a plurality of headercompression profiles. Each profile indicates a specific protocolcombination and a profile identifier identifying each profile can beallocated by the Internet assigned numbers authority. Some of theprofiles shown in FIG. 24 can be used in the broadcast system accordingto embodiments of the present invention.

FIG. 25 illustrates processes of configuring and recovering an RoHCpacket stream with respect to configuration mode #1 according to anembodiment of the present invention.

A description will be given of an RoHC packet stream configurationprocess in a transmitter according to an embodiment of the presentinvention.

The transmitter according to an embodiment can detect IR packets andIR-DYN packets from an RoHC packet stream L10010 on the basis of RoHCheader information. Then the transmitter can generate general headercompressed packets using sequence numbers included in the IR packets andthe IR-DYN packets. The general header compressed packets can berandomly generated since the general header compressed packets includesequence number (SN) information irrespective of the type thereof. Here,the SN corresponds to information that is basically present in the RTP.In the case of the UDP, the transmitter can generate and use the SN. Thetransmitter can replace the IR packets or the IR-DYN packets with thegenerated general header compressed packets, extract a static chain anda dynamic chain from the IR packets and extract a dynamic chain from theIR-DYN packets. The extracted static chain and dynamic chain can betransported through out-of-band L10030. The transmitter can replace IRheaders and IR-DYN headers with headers of general header compressedpackets and extract static chains and/or dynamic chains, for all RoHCpacket streams, according to the aforementioned process. A reconfiguredpacket stream L10020 can be transmitted through a data pipe and theextracted static chain and dynamic chain can be transported throughout-of-band L10030.

A description will be given of a process of recovering an RoHC packetstream in a receiver according to an embodiment of the presentinvention.

The receiver according to an embodiment of the present invention canselect a data pipe corresponding to a packet stream to be received usingsignaling information. Then, the receiver can receive the packet streamtransmitted through the data pipe (S10040) and detect a static chain anda dynamic chain corresponding to the packet stream. Here, the staticchain and/or the dynamic chain can be received through out-of-band(S10050). Subsequently, the receiver can detect general headercompressed packets having the same SN as that of the static chain or thedynamic chain from the packet stream transmitted through the data pipe,using SNs of the detected static chain and the dynamic chain. Thereceiver can configure IR packets and/or IR-DYN packets by combining thedetected general header compressed packets with the static chain and/orthe dynamic chain. The configured IR packets and/or the IR-DYN packetscan be transmitted to an RoHC decompressor. In addition, the receivercan configure an RoHC packet stream L10060 including the IR packets, theIR-DYN packets and/or the general header compressed packets. Theconfigured RoHC packet stream can be transmitted to the RoHCdecompressor. The receiver according to an embodiment of the presentinvention can recover the RoHC packet stream using the static chain, thedynamic chain, SNs and/or context IDs of the IR packets and the IR-DYNpackets.

FIG. 26 illustrates processes of configuring and recovering an RoHCpacket stream with respect to configuration mode #2 according to anembodiment of the present invention.

A description will be given of an RoHC packet stream configurationprocess in a transmitter according to an embodiment of the presentinvention.

The transmitter according to an embodiment can detect IR packets andIR-DYN packets from an RoHC packet stream L11010 on the basis of RoHCheader information. Then the transmitter can generate general headercompressed packets using sequence numbers included in the IR packets andthe IR-DYN packets. The general header compressed packets can berandomly generated since the general header compressed packets includesequence number (SN) information irrespective of the type thereof. Here,the SN corresponds to information that is basically present in the RTP.In the case of the UDP, the transmitter can generate and use the SN. Thetransmitter can replace the IR packets or the IR-DYN packets with thegenerated general header compressed packets, extract a static chain fromthe IR packets and extract a dynamic chain from the IR-DYN packets. Theextracted static chain and dynamic chain can be transported throughout-of-band L11030. The transmitter can replace IR headers and IR-DYNheaders with headers of general header compressed packets and extractstatic chains and/or dynamic chains, for all RoHC packet streams,according to the aforementioned process. A reconfigured packet streamL11020 can be transmitted through a data pipe and the extracted staticchain and dynamic chain can be transported through out-of-band L11030.

A description will be given of a process of recovering an RoHC packetstream in a receiver according to an embodiment of the presentinvention.

The receiver according to an embodiment of the present invention canselect a data pipe corresponding to a packet stream to be received usingsignaling information. Then, the receiver can receive the packet streamtransmitted through the data pipe (S11040) and detect a static chain anda dynamic chain corresponding to the packet stream. Here, the staticchain and/or the dynamic chain can be received through out-of-band(S11050). Subsequently, the receiver can detect general headercompressed packets having the same SN as that of the static chain or thedynamic chain from the packet stream transmitted through the data pipe,using SNs of the detected static chain and the dynamic chain. Thereceiver can configure IR packets and/or IR-DYN packets by combining thedetected general header compressed packets with the static chain and/orthe dynamic chain. The configured IR packets and/or the IR-DYN packetscan be transmitted to an RoHC decompressor. In addition, the receivercan configure an RoHC packet stream L11060 including the IR packets, theIR-DYN packets and/or the general header compressed packets. Theconfigured RoHC packet stream can be transmitted to the RoHCdecompressor. The receiver according to an embodiment of the presentinvention can recover the RoHC packet stream using the static chain, thedynamic chain, SNs and/or context IDs of the IR packets and the IR-DYNpackets.

FIG. 27 illustrates processes of configuring and recovering an RoHCpacket stream with respect to configuration mode #2 according to anembodiment of the present invention.

A description will be given of an RoHC packet stream configurationprocess in a transmitter according to an embodiment of the presentinvention.

The transmitter according to an embodiment can detect IR packets from anRoHC packet stream L12010 on the basis of RoHC header information. Then,the transmitter can extract a static chain from the IR packets andconvert the IR packets into IR-DYN packets using parts of the IR packetsother than the extracted static chain. The transmitter can replaceheaders of IR packets with headers of IR-DYN packets and extract staticchains, for all RoHC packet streams, according to the aforementionedprocess. A reconfigured packet stream L12020 can be transmitted througha data pipe and the extracted static chain can be transported throughout-of-band L12030.

A description will be given of a process of recovering an RoHC packetstream in a receiver according to an embodiment of the presentinvention.

The receiver according to an embodiment of the present invention canselect a data pipe corresponding to a packet stream to be received usingsignaling information. Then, the receiver can receive the packet streamtransmitted through the data pipe (S12040) and detect a static chaincorresponding to the packet stream. Here, the static chain can bereceived through out-of-band (S12050). Subsequently, the receiver candetect IR-DYN packets from the packet stream transmitted through thedata pipe. Then, the receiver can configure IR packets by combining thedetected IR-DYN packets with the static chain. The configured IR packetscan be transmitted to an RoHC decompressor. In addition, the receivercan configure an RoHC packet stream L12060 including the IR packets, theIR-DYN packets and/or general header compressed packets. The configuredRoHC packet stream can be transmitted to the RoHC decompressor. Thereceiver according to an embodiment of the present invention can recoverthe RoHC packet stream using the static chain, SNs and/or context IDs ofthe IR-DYN packets.

FIG. 28 shows combinations of information that can be transported out ofband according to an embodiment of the present invention.

According to an embodiment of the present invention, methods fortransporting a static chain and/or a dynamic chain, extracted in an RoHCpacket stream configuration process, out of band may include a methodfor transporting a static chain and/or a dynamic chain through signalingand a method for transporting a static chain and/or a dynamic chainthrough a data pipe through which parameters necessary for systemdecoding are delivered. In an embodiment of the present invention, thedata pipe through which parameters necessary for system decoding aredelivered may be called a base data pipe (DP).

As shown in the figure, the static chain and/or the dynamic chain can betransported through signaling or the base DP. In an embodiment of thepresent invention, transport mode #1, transport mode #2 and transportmode #3 can be used for configuration mode #1 or configuration mode #2and transport mode #4 and transport mode #5 can be used forconfiguration mode #3.

According to an embodiment of the present invention, the configurationmodes and the transport modes may be switched through additionalsignaling according to system state, and only one configuration mode andtransport mode can be fixed and used according to system design.

As shown in the figure, the static chain and the dynamic chain can betransmitted through signaling and a general header compressed packet canbe transmitted through a normal DP in transport mode #1.

Referring to the figure, the static chain can be transmitted throughsignaling, the dynamic chain can be transmitted through the base DP andthe general header compressed packet can be transmitted through a normalDP in transport mode #2.

As shown in the figure, the static chain and the dynamic chain can betransmitted through the base DP and the general header compressed packetcan be transmitted through a normal DP in transport mode #3.

Referring to the figure, the static chain can be transmitted throughsignaling, the dynamic chain can be transmitted through a normal DP andthe general header compressed packet can be transmitted through a normalDP in transport mode #4.

As shown in the figure, the static chain can be transmitted through thebase DP. the dynamic chain can be transmitted through a normal DP andthe general header compressed packet can be transmitted through a normalDP in transport mode #5. Here, the dynamic chain can be transmittedthrough an IR-DYN packet.

FIG. 29 illustrates a packet transmitted through a data pipe accordingto an embodiment of the present invention.

According to an embodiment of the present invention, it is possible togenerate a link layer packet which is compatible irrespective of changeof a protocol of an upper layer or a lower layer of the link layer bynewly defining a packet structure in the link layer.

The link layer packet according to an embodiment of the presentinvention can be transmitted through a normal DP and/or the base DP.

The link layer packet can include a fixed header, an extended headerand/or a payload.

The fixed header has a fixed size and the extended header has a sizevariable depending on a configuration of a packet of an upper layer. Thepayload is a region in which data of the upper layer is transmitted.

A packet header (fixed header or extended header) can include a fieldindicating the type of the payload of the packet. In the case of thefixed header, first 3 bits of 1 byte correspond to data indicating apacket type of the upper layer and the remaining 5 bits are used as anindicator part. The indicator part can include data indicating a payloadconfiguration method and/or configuration information of the extendedheader and the configuration of the indicator part can be changedaccording to packet type.

The figure shows types of packets of the upper layer, included in thepayload, according to packet type values.

The payload can carry an IP packet and/or an RoHC packet through a DPand carry a signaling packet through the base DP according to systemconfiguration. Accordingly, even when packets of various types aresimultaneously transmitted, a data packet and a signaling packet can bediscriminated from each other by assigning packet type values.

A packet type value of 000 indicates that an IP packet of IPv4 isincluded in the payload.

A packet type value of 001 indicates that an IP packet of IPv6 isincluded in the payload.

A packet type value of 010 indicates that a compressed IP packet isincluded in the payload. The compressed IP packet may include aheader-compressed IP packet.

A packet type value of 110 indicates that a packet including signalingdata is included in the payload.

A packet type value of 111 indicates that a framed packet is included inthe payload.

FIG. 30 illustrates a syntax of a link layer packet structure accordingto an embodiment of the present invention.

FIG. 30 shows the structure of the aforementioned packet transmittedthrough a data pipe. The link layer packet may have a Packet_Type field.

A field following the Packet_Type field can depend on the value of thePacket_Type field. When the Packet_Type field has a value of 000 or 001,as shown in the figure, the Packet_Type field can be followed byLink_Layer_Packet_Header_for_IP( ), that is, a header structure for IPpackets. When the Packet_Type field has a value of 010,Link_Layer_Packet_Header_for_Compressed_IP( ), that is, a headerstructure for compressed IP packets can follow the Packet_Type field.When the Packet_Type field has a value of 011, the Packet_Type field canbe followed by Link_Layer_Packet_Header_for_TS( ), that is, a headerstructure for TS packets. When the Packet_Type field has a value of 110,Link_Layer_Packet_Header_for_Signaling( ), that is, a header structurefor signaling information can follow the Pakcet_Type field. When thePacket_Type field has a value of 111, the Packet_Type field can befollowed by Link_Layer_Packet_Header_for_Framed_Packet( ), that is, aheader structure for framed packets. Other values can be reserved forfuture use. Here, meaning of Packet_Type field values may be changedaccording to embodiments.

The field following the Packet_Type field can be followed byLink_Layer_Packet_Payload( ) which is a link layer packet payload.

FIG. 31 illustrates a link layer packet header structure when an IPpacket is delivered to the link layer according to another embodiment ofthe present invention.

In this case, the link layer packet header includes a fixed header andan extended header. The fixed header can have a length of 1 byte and theextended header can have a fixed length of a variable length. The lengthof each header can be changed according to design.

The fixed header can include a packet type field, a packet configuration(PC) field and/or a count field. According to another embodiment, thefixed header may include a packet type field, a PC field, an LI fieldand/or a segment ID field.

The extended header can include a segment sequence number field and/or asegment length ID field. According to another embodiment, the extendedfield may include a segment sequence number field and/or a last segmentlength field.

The fields of the fixed header will now be described.

The packet type field can indicate the type of a packet input to thelink layer, as described above. When an IP packet is input to the linklayer, the packet type field can have a value of 000B or 001B.

The PC field can indicate the remaining part of the fixed header, whichfollows the PC field, and/or the configuration of the extended header.That is, the PC field can indicate the form into which the input IPpacket has been processed. Accordingly, the PC field can includeinformation on the length of the extended header.

A PC field value of 0 can indicate that the payload of the link layerpacket includes one IP packet or two or more concatenated IP packets.Here, concatenation means that short packets are connected to form apayload.

When the PC field has a value of 0, the PC field can be followed by a4-bit count field. The count field can indicate the number ofconcatenated IP packets corresponding to one payload. The number ofconcatenated IP packets, indicated by the counter field, will bedescribed later.

When the PC field value is 0, the link layer may not include theextended header. However, when the length of the link layer packet needsto be indicated according to an embodiment, a one or two-byte extendedheader can be added. In this case, the extended header can be used toindicate the length of the link layer packet.

A PC field value of 1 can indicate that the link layer packet payloadincludes a segmented packet. Here, segmentation of a packet meanssegmentation of a long IP packet into a plurality of segments. Eachsegmented piece can be called a segment or a segmented packet. That is,when the PC field value is 1, the link layer packet payload can includeone segment.

When the PC field value is 1, the PC field can be followed by a 1-bitlast segment indicator (LI) field and a 3-bit segment ID field.

The LI field can indicate whether the corresponding link layer packetincludes the last segment from among segments. That is, thecorresponding link layer includes the last segment when the LI field hasa value of 1 and the corresponding link layer does not include the lastsegment when the LI field has a value of 0. The LI field can be usedwhen a receiver reconfigures the original IP packet. The LI field mayindicate information about the extended header of the link layer packet.That is, the length of the extended header can be 1 byte when the LIfield value is 0 and 2 bytes when the LI field value is 1. Details willbe described later.

The segment ID field can indicate the ID of a segment included in thecorresponding link layer packet. When one IP packet is segmented intosegments, the segments may be assigned the same ID. The segment IDenables the receiver to recognize that the segments are components ofthe same IP packet when reconfiguring the original IP packet. Since thesegment ID field has a size of 3 bits, segmentation of 8 IP packets canbe simultaneously supported.

When the PC field value is 1, the extended header can be used forinformation about segmentation. As described above, the extended headercan include the segment sequence number field, the segment length IDfield and/or the last segment length field.

The fields of the extended header will now be described.

When the aforementioned LI field has a value of 0, that is, when thelink layer packet does not include the last segment, the extended headercan include the segment sequence number field and/or the segment lengthID field.

The segment sequence number field can indicate sequence numbers ofsegmented packets. Accordingly, link layer packets having segmentsobtained by segmenting one IP packet have different segment sequencenumber fields while having the same segment ID field. Since the segmentsequence number field has a size of 4 bits, the IP packet can besegmented into a maximum of 16 segments.

The segment length ID field can indicate the length of segments otherthan the last segment. Segments other than the last segment may have thesame length. Accordingly. the length of the segments can be representedusing a predetermined length ID. The predetermined length ID can beindicated by the segment length ID field.

Segment lengths can be set according to a packet input size which isdetermined on the basis of an FEC code rate of the physical layer. Thatis, segment lengths can be determined according to the packet input sizeand designated by segment length IDs. To reduce header overhead, thenumber of segment lengths can be limited to 16.

Segment length ID field values according to segment lengths will bedescribed later.

When the physical layer operates irrespective of segment lengths, asegment length can be obtained by adding a minimum segment lengthmin_len to a product of the corresponding segment length ID and a lengthunit Len_Unit. Here, the length unit is a basic unit indicating asegment length and the minimum segment length means a minimum value ofthe segment length. The transmitter and the receiver need to always havethe same length unit and the same minimum segment length, and it isdesirable that the length unit and the minimum segment length not bechanged for efficient system operation. The length unit and the minimumsegment length can be determined in consideration of FEC processingcapability of the physical layer in the system initialization process.

When the aforementioned LI field has a value of 1, that is, when thelink layer packet includes the last segment, the extended header caninclude the segment sequence number field and/or the last segment lengthfield.

The segment sequence number field has been described above.

The last segment length field can directly indicate the length of thelast segment. When one IP packet is segmented into segments havingspecific lengths, the last segment may have a different length fromthose of other segments. Accordingly, the last segment length field candirectly indicate the length of the last segment. The last segmentlength field can represent 1 to 4095 bytes. Bytes indicated by the lastsegment length field may be changed according to embodiments.

FIG. 32 illustrates a syntax of a link layer packet header structurewhen an IP packet is delivered to the link layer according to anotherembodiment of the present invention.

The link layer packet header can include the Packet_Type field and thePC field Payload_Config, as described above.

When the PC field has a value of 0, the PC field can be followed by thecount field.

When the PC field has a value of 1, the PC field can be followed by aLast_Segment_Indicator field, Segment_ID field andSegment_Sequence_Number field. Here, the configuration of the partfollowing the Last_Segment_Indicator field can be changed according tothe value of the Last_Segment_Indicator field. When theLast_Segment_Indicator field is 0, the Segment_Length_ID field canfollow the Segment_Sequence_Number field. When theLast_Segment_Indicator field is 1, the Last_Segment_Length field canfollow the Segment_Sequence_Number field.

FIG. 33 illustrates indication of field values in a link layer packetheader when an IP packet is delivered to the link layer according toanother embodiment of the present invention.

As described above, the number of concatenated IP packets can bedetermined on the basis of a count field value (t61010). While the countfield value can directly indicate the number of concatenated IP packets,the count field value is meaningless when 0 packets are concatenated.Accordingly, the count field can indicate that as many IP packets as thevalue obtained by adding 1 to the count field value have beenconcatenated. That is, a count field value of 0010 can indicate that 3IP packets have been concatenated and a count field value of 0111 canindicate that 8 IP packets have been concatenated as shown in the tablet61010.

A count field value of 0000 indicating that one IP packet has beenconcatenated can represent that the link layer packet payload includesone IP packet without concatenation.

As described above, a segment length can be indicated by a segmentlength ID field value (t61020).

For example, a segment length ID field value of 0000 can indicate asegment length of 512 bytes. This means that a segment included in thecorresponding link layer packet payload is not the last segment and hasa length of 512 bytes. Other segments from the same IP packet may alsohave a length of 512 bytes if the segments are not the last segment.

In the table, the length unit has a value of 256 and the minimum segmentlength has a value of 512. Accordingly, the minimum segment length is512 bytes (segment length ID field=0000). Designated segment lengthsincrease at an interval of 256 bytes.

FIG. 34 illustrates a case in which one IP packet is included in a linklayer payload in a link layer packet header structure when IP packetsare delivered to the link layer according to another embodiment of thepresent invention.

A case in which one IP packet is included in the link layer payload,that is, a case in which concatenation or segmentation is not performedmay be referred to as encapsulation into a normal packet. In this case,the IP packet is within a processing range of the physical layer.

In the present embodiment, the link layer packet has a 1-byte header.The header length may be changed according to embodiments. The packettype field may have a value of 000 (in the case of IPv4) or 001 (in thecase of IPv6). Normal packet encapsulation can be equally applied toIPv4 and IPv6. The PC field value can be 0 since one packet is includedin the payload. The count field following the PC field can have a valueof 0000 since only one packet is included in the payload.

In the present embodiment, the link layer packet payload can include onewhole IP packet.

In the present embodiment, information of the IP packet header can beused to confirm the length of the link layer packet. The IP packetheader includes a field indicating the length of the IP packet. Thisfield can be called a length field. The length field may be located at afixed position in the IP packet. Since the link layer payload includesone whole IP packet, the length field can be located at a position at adistance from the starting point of the link layer packet payload by apredetermined offset. Accordingly, the length of the link layer payloadcan be recognized using the length field.

The length field can be located at a position at a distance from thestarting point of the payload by 4 bytes in the case of IPv4 and at aposition at a distance from the starting point of the payload by 2 bytesin the case of IPv6. The length field can have a length of 2 bytes.

In the case of IPv4, when the length field value is L_(IPv4) and thelink layer packet header length is L_(H) (1 byte), the total length ofthe link layer packet, L_(T), can be represented by an equation t62010shown in the figure. Here, the length field value LIPv4 can indicate thelength of the IPv4 packet.

In the case of IPv6. when the length field value is L_(IPv6) and thelink layer packet header length is L_(H) (1 byte), the total link layerpacket length L_(T) can be represented by an equation t62020 shown inthe figure. Here, since the length field value L_(IPv6) indicates onlythe length of the IPv6 packet payload, the length (40 bytes) of thefixed header of the IPv6 packet needs to be added to the length fieldvalue in order to obtain the length of the link layer packet.

FIG. 35 illustrates a case in which multiple IP packets are concatenatedand included in a link layer payload in a link layer packet headerstructure when IP packets are delivered to the link layer according toanother embodiment of the present invention.

When input IP packets are not within the processing range of thephysical layer, multiple IP packets may be concatenated and encapsulatedinto a payload of one link layer packet.

In the present embodiment, the link layer packet can have a 1-byteheader. The header length may be changed according to embodiments. Thepacket type field can have a value of 000 (in the case of IPv4) or 001(in the case of IPv6). The encapsulation process of the presentembodiment can be equally applied to IPv4 and IPv6. The PC field valuecan be 0 since the concatenated IP packets are included in the payload.The count field following the PC field (4 bits) can indicate the numberof concatenated IP packets.

In the present embodiment, the link layer packet payload can includemultiple IP packets. The multiple IP packets can be sequentiallyconcatenated and included in the link layer packet payload. Theconcatenation method can be changed according to design.

In the present embodiment, to confirm the length of the link layerpacket, information of headers of the concatenated IP packets can beused. As in the aforementioned normal packet encapsulation, the headerof each IP packet may have the length field indicating the length of theIP packet. The length field can be located at a fixed position in thecorresponding IP packet.

Accordingly, when the header length of the link layer packet is L_(H)and the length of each IP packet is L_(K) (K being equal to or greaterthan 1 and equal to or less than n), the total length of the link layerpacket length, L_(T), can be represented by an equation t63010 shown inthe figure. That is, the link layer packet length can be obtained bysumming the lengths of the IP packets, respectively indicated by thelength fields of the IP packets, and adding the header length of thelink layer packet to the sum. L_(K) can be confirmed by reading thelength fields of the headers of the respective IP packets.

FIG. 36 illustrates a case in which one IP packet is segmented andincluded in a link layer payload in a link layer packet header structurewhen IP packets are delivered to the link layer according to anotherembodiment of the present invention.

When input IP packets exceed the processing range of the physical layer,one IP packet may be segmented into a plurality of segments. Thesegments can be respectively encapsulated in payloads of link layerpackets.

In the present embodiment, link layer packets t64010, t64020 and t64030can have fixed headers and extended headers. The fixed header length andextended header length may be changed according to embodiments. Thepacket type field value can be 000 (in the case of IPv4) or 001 (in thecase of IPv6). The encapsulation process of the present embodiment canbe equally applied to IPv4 and IPv6. The PC field value can be 1 sincethe segments are included in the payloads.

The link layer packets t64010 and t64020 including segments, which arenot the last segment, in the payloads thereof can have an LI field valueof 0 and the same segment ID field value since the segments are from thesame IP packet. The segment sequence number field following the segmentID field can indicate the sequence of the corresponding segment. Here,the segment sequence field value of the first link layer packet t64010can indicate that the link layer packet has the first segment as apayload. The segment sequence field value of the second link layerpacket t64020 can indicate that the link layer packet has the secondsegment as a payload. The segment length ID field can represent thelength of the corresponding segment as a predetermined length ID.

The link layer packet t64030 having the last segment as a payload mayhave an LI field value of 1. The segment ID field can have the samevalue as those of other link layer packets since the last segment isalso from the same IP packet. The segment sequence number fieldfollowing the segment ID field can indicate the sequence of thecorresponding segment. The last segment length field can directlyindicate the length of the last segment included in the link layerpacket t64030.

In the present embodiment, to confirm the length of a link layer packet,the segment length ID field or the last segment length field can beused. Since the fields indicate only the length of the payload of thelink layer packet, the header length of the link layer packet needs tobe added thereto in order to obtain the length of the link layer packet.The header length of the link layer packet can be detected from the LIfield, as described above.

FIG. 37 illustrates link layer packets having segments in a link layerpacket header structure when IP packets are transmitted to the linklayer according to another embodiment of the present invention.

The present embodiment assumes that a 5500-byte IP packet is input.Since the value obtained by dividing 5500 by 5 is 1100, the IP packetcan be segmented into segments each having a length of 1024 bytes closesto 1100. In this case, the last segment can be 1404 bytes(010101111100B). The segments can be respectively referred to as S1, S2,S3, S4 and S5 and headers corresponding thereto can be respectivelyreferred to as H1, H2, H3, H4 and H5. The headers can be respectivelyadded to the segments to generate respective link layer packets.

When the input IP packet is an IPv4 packet, the packet type fields ofthe headers H1 to H5 can have a value of 000. The PC fields of theheaders H1 to H5 can have a value of 1 since the link layer packets havethe segments of the packet as payloads.

LI fields of the headers H1 to H4 can have a value of 0 since thecorresponding link layer packets do not have the last segment as apayload. The LI field of the header H5 can have a value of 1 since thecorresponding link layer packet has the last segment as a payload. Thesegment ID fields, Seg_ID, of the headers H1 to H5 can have the samevalue, 000, since the corresponding link layer packets have segmentsfrom the same packet as payloads.

The segment sequence number fields, Seg_SN, of the headers H1 to H5 canbe sequentially represented as 0000B to 0100B. The segment length IDfields of the headers HI to H4 can have a value of 0010 corresponding toan ID that is 1024 bytes in length. The segment length ID field of theheader H5 can have a value of 010101111100 which indicates 1404 bytes.

FIG. 38 illustrates a header of a link layer packet for RoHCtransmission according to an embodiment of the present invention.

Even in an IP based broadcast environment, an IP packet can becompressed into a link layer packet and transmitted. When an IP basedbroadcast system streams IP packets, header information of the IPpackets can generally remain unchanged. Using this fact, IP packetheaders can be compressed.

Robust header compression (RoHC) is mainly used to compress an IP packetheader (IP header). The present invention proposes an encapsulationmethod when RoHC packets are input to the link layer.

When RoHC packets are input to the link layer, the aforementioned packettype element may have a value of 010_(B), which indicates that a packetdelivered from an upper layer to the link layer is a compressed IPpacket.

When RoHC packets are input, the header of the link layer packet caninclude a fixed header and/or an extended header like the aforementionedother packets.

The fixed header can include a packet type field and/or a packetconfiguration (PC) field. The fixed header may have a size of 1 byte.Here, the packet type field can have a value of 010 since the inputpacket is a compressed IP packet. The extended header can have a fixedsize or a variable size according to embodiments.

The PC field of the fixed header can indicate a form into which RoHCpackets constituting the link layer packet payload are processed.Information of the remaining part of the fixed header, which follows thePC field, and the extended header can be determined by the value of thePC field. In addition, the PC field can include information on thelength of the extended header according to the form into which RoHCpackets are processed. The PC field can have a size of 1 bit.

A description will be given of a case in which the PC field has a valueof 0_(B).

When the PC field has a value of 0_(B), the link layer packet payload iscomposed of one RoHC packet or two or more concatenated RoHC packets.Concatenation refers to connecting a plurality of short packets toconfigure a link layer packet payload.

When the PC field has a value of 0_(B), the PC field can be followed bya 1-bit common context ID indicator (CI) field and a 3-bit count field.Accordingly, common CID information and a length part can be added tothe extended header. The length part can indicate the length of an RoHCpacket.

The CI field can be set to 1 when RoHC packets constituting the payloadof one link layer packet have the same context ID (CID) and set to 0otherwise. When the CI field has a value of 1, an overhead processingmethod for a common CID can be applied. The CI field can be 1 bit.

The count field can indicate the number of RoHC packets included in thepayload of one link layer packet. That is, when RoHC packets areconcatenated, the number of concatenated RoHC packets can be indicatedby the count field. The count filed can be 3 bits. Accordingly, amaximum of 8 RoHC packets can be included in the payload of one linklayer packet, as shown in the following table. A count field value of000 indicates that the link layer packet payload is composed of one RoHCpacket rather than multiple concatenated RoHC packets.

Count (3bits) No. of Concatenated RoHC packets 000 1 001 2 010 3 011 4100 5 101 6 110 7 111 8

The length part can indicate an RoHC packet length, as described above.The RoHC packet has a header from which length information has beenremoved, and thus the length field in the RoHC packet header cannot beused. Accordingly, the header of the link layer packet can include thelength part in order to enable the receiver to recognize the length ofthe corresponding RoHC packet.

An IP packet has a maximum of 65535-byte length when an MTU is notdetermined. Accordingly, 2-byte length information is necessary for theRoHC packet such that a maximum length thereof can be supported. Whenmultiple RoHC packets are concatenated, as many length fields as thenumber designated by the count field can be added. In this case, thelength part includes a plurality of length fields. However, when oneRoHC packet is included in the payload, only one length field can beincluded in the length part. Length fields can be arranged in the sameorder as that of RoHC packets constituting the link layer packetpayload. Each length field can be a value in bytes.

A common CID field is a field through which a common CID is transmitted.The header of the RoHC packet may include a context ID (CID) used tocheck the relation between compressed headers. The CID can be maintainedas the same value in a stable link state. Accordingly, all RoHC packetsincluded in the payload of one link layer packet may include the sameCID. In this case, to reduce overhead, it is possible to remove the CIDfrom the headers of concatenated RoHC packets constituting the payload,indicate the CID in the common CID field of the header of the link layerpacket and transmit the link layer packet. The receiver can reconfigurethe CID of the RoHC packets using the common CID field. When the commonCID field is present, the aforementioned CI field needs to have a valueof 1.

A description will be given of a case in which the PC field has a valueof 1_(B).

A PC field value of 1_(B) indicates that a link layer packet payload iscomposed of segmented packets of an RoHC packet. Here, a segmentedpacket refers to a segment from among a plurality of segments obtainedby segmenting a long RoHC packet. One segment constitutes a link layerpacket payload.

When the PC field has a value of 1_(B), the PC field can be followed bya 1-bit last segment indicator (LI) field and a 3-bit segment ID field.To add information about segmentation, a segment sequence number field,a segment length ID field and a last segment length field may be addedto the extended header.

The LI field can be used when an RoHC packet is segmented. An RoHCpacket can be segmented into a plurality of segments. An LI field valueof 1 can indicate that a segment included in the current link layerpacket is the last segment from among segments obtained from one RoHCpacket. An LI field value of 0 can indicate that a segment included inthe current link layer packet is not the last segment. The LI field canbe used when the receiver determines whether all segments have beenreceived when reconfiguring one RoHC packet by combining segments. TheLI field can be 1 bit.

The segment ID field Seg_ID can indicate an ID assigned to an RoHCpacket when the RoHC packet is segmented. Segments derived from one RoHCpacket can have the same segment ID. The receiver can determine whethersegments transmitted thereto are components of the same RoHC packetusing the segment ID when combining the segments. The segment ID fieldcan be 3 bits. Accordingly, the segment ID field can simultaneouslysupport segmentation of 8 RoHC packets.

The segment sequence number field Seg_SN can be used to check thesequence of segments when an RoHC packet is segmented. That is, linklayer packets having segments derived from one RoHC packet as payloadthereof may have different segment sequence number fields while havingthe same sequence ID field. Accordingly, one RoHC packet can besegmented into a maximum of 16 segments.

The segment length ID field Seg_Len_ID can be used to represent thelength of each segment. However, the segment length ID field can be usedto indicate the length of segments other than the last segment fromamong a plurality of segments. The length of the last segment can beindicated by the last segment length field which will be describedlater. When a link layer packet payload does not correspond to the lastsegment of an RoHC packet, that is, when the LI field is 0, the segmentlength ID field can be present.

To reduce header overhead, the number of segment lengths can be limitedto 16. A packet input size may be determined according to code rate ofFEC processed in the physical layer. Segment lengths can be determinedaccording to the packet input size and designated by Seg_Len_ID. Whenthe physical layer operates irrespective of segment lengths, a segmentlength can be determined as follows.Segment Length=Seg_Len_ID×Len_Unit+min_Len [bytes]  [Equation 1]

Here, a length unit Len_Unit is a basic unit indicating a segment lengthand min_Len indicates a minimum segment length. The transmitter and thereceiver need to have the same Len_Unit and the same min_Len. It isefficient for system operation that Len_Unit and the same min_Len arenot changed after being determined once. Furthermore, Len_Unit andmin_Len can be determined in consideration of FEC processing capabilityof the physical layer in the system initialization process.

The following table shows segment lengths represented according toSeg_Len_ID values. A length allocated to Seg_Len_ID can be changedaccording to design. In the present embodiment, Len_Unit is 256 andmin_Len is 512.

TABLE 2 Segment Segment Seg_Len_ID Length (byte) Seg_Len_ID Length(byte) 0000 512 (=min_Len) 1000 2560 0001 768 1001 2816 0010 1024 10103072 0011 1280 1011 3328 0100 1536 1100 3584 0101 1792 1101 3840 01102048 1110 4096 0111 2304 1111 4352

The last segment length field L_Seg_Len is used when a segment includedin a link layer packet payload is the last segment of the correspondingRoHC packet. That is, the last segment length field is used when the LIfield has a value of 1. An RoHC packet can be segmented into segments ofthe same size using Seg_Len_ID. In this case, however, the last segmentmay not have the size indicated by Seg_Len_ID. Accordingly, the lengthof the last segment can be directly indicated by the last segment lengthfield. The last segment length field can indicate 1 to 4095 bytes. Thiscan be changed according to embodiments.

FIG. 39 illustrates a syntax of a header of a link layer packet for RoHCpacket transmission according to an embodiment of the present invention.

The link layer packet header may include the Packet_Type field and thePC field Payload_Config, which have been described above.

When the PC field has a value of 0, the PC field can be followed by aCommon_ContextID_Indication field and a count field. A plurality oflength fields can be included in the link layer packet on the basis of avalue indicated by the count field. When the CI field is 1, a Common_CIDfield can be additionally included in the link layer packet header.

When the PC field is 1, the PC field can be followed by aLast_Segment_Indicator field, a Segment_ID field and aSegment_Sequence_Number field. A configuration of the part following theLast_Segment_Indicator field can be changed according to the value ofthe Last_Segment_Indicator field. When the Last_Segment_Indicator fieldis 0, the Segment_Sequence_Number field can be followed by theSegment_Length_ID field. When the Last_Segment_Indicator field is 1, theSegment_Sequence_Number field can be followed by the Last_Segment_Lengthfield.

FIG. 40 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #1 of the present invention.

The present embodiment corresponds to a case in which one RoHC packetconstitutes a link layer packet payload since the RoHC packet is withina processing range of the physical layer. Here, the RoHC packet may notbe concatenated or segmented.

In this case, one RoHC packet can become a link layer packet payload.The packet type field can be 010_(B), the PC field can be 0_(B) and theCI field can be 0_(B). The aforementioned count field can be 000_(B)since one RoHC packet constitutes the payload (the number of RoHCpackets constituting the payload being 1). The count field can befollowed by a 2-byte length field indicating the length of the RoHCpacket. In this case, the length part can include only one length fieldsince only one packet constitutes the payload.

In the present embodiment, a 3-byte link layer header can be added.Accordingly, when the length of the RoHC packet, indicated by the lengthfield, is L bytes, the length of the link layer packet is L+3 bytes.

FIG. 41 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #2 of the present invention.

The present embodiment corresponds to a case in which an RoHC packetdoes not exceed the processing range of the physical layer and thusmultiple RoHC packets are concatenated and included in a payload of alink layer packet.

In this case, the PC field and the CI field have same values as those ina case in which one RoHC packet is included in a link layer packetpayload. The CI field is followed by the count field. The count fieldcan have a value in the range of 001_(B) to 111_(B) on the basis of thenumber of RoHC packets included in the payload, as described above.

The count field can be followed by as many 2-byte length fields as thenumber indicated by the count field. Each length field can indicate thelength of each RoHC packet. The length fields can be called a lengthpart.

When the count field indicates n, RoHC packets R₁, R₂, . . . , R_(n),respectively having lengths L₁, L₂, . . . , L_(n), can be concatenatedin the link layer packet payload.

The extended header can have a length of 2n bytes. The total length ofthe link layer packet, L_(T), can be represented by the followingequation.

$\begin{matrix}{L_{T} = {1 + {2n} + {\sum\limits_{k = 1}^{n}\;{L_{k}\mspace{14mu}\lbrack{bytes}\rbrack}}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

FIG. 42 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #3 of the present invention.

The present embodiment corresponds to a case in which RoHC packets areconcatenated to constitute a payload of a link layer packet and the RoHCpackets have the same CID.

When the RoHC packets have the same CID, even if the CID is indicatedonly once through the link layer packet and transmitted to the receiver,the receiver can recover the original RoHC packets and headers thereof.Accordingly, a common CID can be extracted from the RoHC packets andtransmitted, reducing overhead.

In this case, the aforementioned CI field becomes 1, which representsthat processing for the same CID has been performed. The RoHC packetshaving the same CID are indicated by [R1, R2, R3, . . . , Rn]. The sameCID is referred to as a common CID. Packets other than CIDs in RoHCpacket headers are referred to as R′k (k being 1, 2, . . . , n).

The link layer packet payload can include R′k (k being 1, 2, . . . , n).A common CID field can be added to the end of the extended header of thelink layer packet. The common CID field may be a field for common CIDtransmission. The common CID field may be transmitted as a part of theextended header or a part of the link layer packet payload. It ispossible to rearrange the common CID field in a part in which theposition of the common CID field can be identified according to systemoperation.

The size of the common CID field can depend on RoHC packetconfiguration.

When the RoHC packet configuration is a small CID configuration, the CIDof an RoHC packet can be 4 bits. However, when the CID is extracted fromthe RoHC packet and rearranged, the entire add-CID octet can beprocessed. That is, the common CID field can have a length of 1 byte.Alternatively, it is possible to extract a 1-byte add-CID octet from theRoHC packet, allocate only a 4-bit CID to the common CID field andreserve the remaining 4 bits for future use.

When the RoHC packet configuration is a large CID configuration, the CIDof an RoHC packet can be 1 byte or 2 bytes. The CID size is determinedin the RoHC initialization process. The common CID field can have alength of 1 byte or 2 bytes depending on the CID size.

In the present embodiment, the link layer packet payload can becalculated as follows. n RoHC packets R₁, R₂, . . . , R_(n) having thesame CID are respectively referred to as L₁, L2, . . . , L_(n). When thelength of the link layer packet header is L_(H), the length of thecommon CID field is L_(CID) and the total length of the link layerpacket is L_(T), L_(H) is calculated as follows.L _(H)=1+2n+L _(CID) bytes  [Equation 3]

L_(T) can be calculated as follows.

$\begin{matrix}{L_{T} = {L_{H} + {\sum\limits_{k = 1}^{n}\;{\left( {L_{k} - L_{CID}} \right)\mspace{20mu}{bytes}}}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

As described above, L_(CID) can be determined according to CIDconfiguration of RoHC. That is, L_(CID) can be 1 byte in the case of asmall CID configuration and 1 byte or 2 bytes in the case of a large CIDconfiguration.

FIG. 43 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #4 of the present invention.

The present embodiment corresponds to a case in which an input RoHCpacket exceeds the processing range of the physical layer and thus theRoHC packet is segmented and the segments of the RoHC packet arerespectively encapsulated into link layer packet payloads.

To indicate that the link layer packet payloads are composed ofsegmented RoHC packets, the PC field can be 1_(B). The LI field becomes1_(B) only in a link layer packet having the last segment of the RoHCpacket as a payload and becomes 0_(B) for the remaining segments. The LIfield also indicates information about the extended header of thecorresponding link layer packet. That is, a 1-byte extended header canbe added when the LI field is 0_(B) and a 2-byte extended header can beadded when the LI field is 1_(B).

The link layer packets need to have the same Seg_ID value in order toindicate that the segments have been derived from the same RoHC packet.To indicate the order of segments for normal RoHC packet reconfigurationin the receiver, a sequentially increasing Seg_SN value can be includedin corresponding headers.

When the RoHC packet is segmented, a segment length can be determined,as described above, and segmentation can be performed. A Seg_Len_IDvalue corresponding to the segment length can be included in thecorresponding headers. The length of the last segment can be directlyincluded in a 12-bit L_Seg_Len field, as described above.

Length information indicated using the Seg_Len_ID and L_Seg_Len fieldsrepresents only information about a segment, that is, a payload of alink layer packet. Accordingly, the total length of the link layerpacket can be calculated by adding the header length of the link layerpacket, which can be detected from the LI field, to the length of thelink layer packet payload.

When the receiver reconfigures the segments of the RoHC packet, it isnecessary to check integrity of the reconfigured RoHC packet. To thisend, a CRC can be added to the end of the RoHC packet in a segmentationprocess. Since the CRC is generally added to the end of the RoHC packet,the CRC can be included in the segment after segmentation.

FIG. 44 illustrates a link layer packet structure when signalinginformation is delivered to the link layer according to anotherembodiment of the present invention.

In this case, the header of the link layer packet can include a fixedheader and an extended header. The fixed header can have a length of 1byte and the extended header can have a fixed length or a variablelength. The length of each header can be changed according to design.

The fixed header can include a packet type field, a PC field and/or aconcatenation count field. According to another embodiment, the fixedheader may include the packet type field, the PC field, an LI fieldand/or a segment ID field.

The extended header can include a signaling class field, an informationtype field and/or a signaling format field. According to anotherembodiment, the extended header may further include a payload lengthpart. According to another embodiment, the extended header may include asegment sequence number field, a segment length ID field, the signalingclass field, the information type field and/or the signaling formatfield. According to another embodiment, the extended header may includethe segment sequence number field and/or the segment length ID field.According to another embodiment, the extended header may include thesegment sequence number field and/or a last segment length field.

The fields of the fixed header will now be described.

The packet type field can indicate the type of a packet input to thelink layer, as described above. When signaling information is input tothe link layer, the packet type field can be 110B.

The PC field, the LI field, the segment ID field, the segment sequencenumber field, the segment length ID field and the last segment field areas described above. The concatenation count field is as described above.

Description will be given of the fields of the extended header.

When the PC field is 0, the extended header can include the signalingclass field, the information type field and/or the signaling formatfield. The extended header may further include a length part accordingto the value of the signaling format field.

The signaling class field can indicate the type of signaling informationincluded in the link layer packet. Signaling information that can beindicated by the signaling class field can include fast informationchannel (FIC) information, header compression information and the like.The signaling information that can be indicated by the signaling classfield will be described later.

The information type field can indicate details of signaling informationof the type indicated by the signaling class field. Indication of theinformation type field can be separately defined according to the valueof the signaling class field.

The signaling format field can indicate a format of signalinginformation included in the link layer packet. Formats that can beindicated by the signaling format field may include a section table, adescriptor, XML and the like. The formats that can be indicated by thesignaling format field will be described later.

A payload length part can indicate the length of signaling informationincluded in the payload of the link layer packet payload. The payloadlength part may be a set of length fields respectively indicatinglengths of concatenated signaling information. While each length fieldmay have a size of 2 bytes, the size can be changed according to systemconfiguration. The total length of the payload length part can berepresented by the sum of the respective length fields. A padding bitfor byte arrangement can be added to the payload length part accordingto an embodiment. In this case, the total length of the payload lengthpart can increase by the padding bit.

Presence or absence of the payload length part can be determined by thesignaling format field value. When signaling information has a lengthvalue thereof, such as the section table and descriptor, an additionallength field may not be needed. However, signaling information having nolength value may require an additional length field. In the case ofsignaling information having no length value, the payload length partcan be present. In this case, the payload length part can include asmany length fields as the number of count fields.

When the PC field is 1 and the LI field is 1, the extended header caninclude the segment sequence number field and/or the last segment lengthfield. When the PC field is 1 and the LI field is 0, the extended headercan include the segment sequence number field and/or the segment lengthID field.

The segment sequence number field, the last segment length field and thesegment length ID field are as described above.

When the PC field is 1, the LI field is 1 and the payload of thecorresponding link layer packet corresponds to the first segment, theextended header of the link layer packet can further include additionalinformation. The additional information can include the signaling classfield, the information type field and/or the signaling format field. Thesignaling class field, the information type field and the signalingformat field are as described above.

FIG. 45 illustrates a syntax of a link layer packet structure whensignaling information is delivered to the link layer according toanother embodiment of the present invention.

The link layer packet header can include the Packet_Type field and thePC field Payload_Config, as described above.

When the PC field is 0, the PC field can be followed by a Count field, aSignaling_Class field, an Information_Type field and a Signaling_Formatfield. When the Signaling_Format field is 1× (10 or 11), a plurality oflength fields can be included in the link layer packet header on thebasis of a value indicated by the count field.

When the PC field is 1, the PC field can be followed by aLast_Segment_Indicator field, a Segment_ID field and aSegment_Sequence_Number field. Here, a configuration of a part followingthe Last_Segment_Indicator field can be changed according to the valueof the Last_Segment_Indicator field.

When the Last_Segment_Indicator field is 0, the Segment_Sequence_Numberfield can be followed by the Segment_Length_ID field. When theSegment_Sequence_Number field is 0000, the Segment_Sequence_Number fieldcan be followed by the Signaling_Class field, the Information_Type fieldand the Signaling_Format field.

When the Last_Segment_Indicator field is 1, the Segment_Sequence_Numberfield can be followed by the Last_Segment_Length field.

FIG. 46 illustrates a structure of a link layer packet for framed packettransmission according to an embodiment of the present invention.

Packets used in normal networks, other than the IP packet and MPEG-2 TSpacket, can be transmitted through a link layer packet. In this case,the packet type element of the header of the link layer packet can havea value of 111B to indicate that the payload of the link layer packetincludes a framed packet.

FIG. 47 illustrates a syntax of a structure of a link layer packet forframed packet transmission according to an embodiment of the presentinvention.

The link layer packet header can include the Packet_Type field, asdescribed above. The link layer packet header can include 5 bitsreserved for future use after the Packlet_Type field. A framed packetindicated by framed_packet( ) can follow the reserved bits.

FIG. 48 illustrates a syntax of a framed packet according to anembodiment of the present invention.

The syntax of the framed packet can include an Ethernet_type field, alength field, and/or a packet( ) field. The Ethernet_type field, whichis 16 bits, can indicate the type of a packet in the packet( ) fieldaccording to IANA registry. Here, only registered values can be used.The length field, which is 16 bits, can set the total length of thepacket structure in bytes. The packet( ) field having a variable lengthcan include a network packet.

FIG. 49 illustrates a syntax of a fast information channel (FIC)according to an embodiment of the present invention.

Information included in the FIC can be transmitted in the form of a fastinformation table (FIT).

Information included in the FIT can be transmitted in the form of XMLand/or a section table.

The FIC can include FIT_data_version information, num_broadcastinformation, broadcast_id information, delivery_system_id information,base_DP_id information, base_DP_version information, num_serviceinformation, service_id information, service_category information,service_hidden_flag information, SP_indicator information, num_componentinformation, component_id information, DP_id information and/orRoHC_init_descriptor information.

The FIT_data_version information can indicate version information abouta syntax and semantics included in the fast information table. Thereceiver can determine whether to process signaling included in the fastinformation table using the FIT_data_version information. The receivercan determine whether to update prestored information of the FIC usingthe FIT_data_version information.

The num_broadcast information can indicate the number of broadcastingstations which transmit broadcast services and/or content throughcorresponding frequencies or transmitted transport frames.

The broadcast_id information can indicate identifies of broadcastingstations which transmit broadcast services and/or content throughcorresponding frequencies or transmitted transport frames. Abroadcasting station transmitting MPEG-2 TS based data may have abroadcast_id identical to a transport_stream_id of an MPEG-2 TS.

The delivery_system_id information can indicate an identifier of abroadcast transmission system which performs processing using the sametransmission parameter on a broadcast network.

The base_DP_id information indicates a base DP in a broadcast signal.The base DP can refer to a DP conveying service signaling includingprogram specific information (PSI)/system information (SI) and/oroverhead reduction of a broadcasting station corresponding to thebroadcast_id. Otherwise, the base DP can refer to a representative DPwhich can be used to decode components constituting broadcast servicesin the corresponding broadcasting station.

The base_DP_version information can indicate version information aboutdata transmitted through the base DP. For example, when servicesignaling such as PSI/IS through the base DP, the value of thebase_DP_version information can increase by 1 if service signalingchanges.

The num_service information can indicate the number of broadcastservices transmitted by the broadcasting station corresponding to thebroadcast_id in the corresponding frequency or transport frame.

The service_id information can be used as an identifier of a broadcastservice.

The service_category information can indicate a broadcast servicecategory. A service_category information value of 0x01 can indicateBasic TV, a service_category information value of 0x02 can indicateBasic Radio, a service_category information value of 0x03 can indicateRI service, a service_category information value of 0x08 can indicateService Guide, and a service_category information value of 0x09 canindicate Emergency Alerting.

The service_hidden_flag information can indicate whether thecorresponding broadcast service is hidden. When the broadcast service ishidden, the broadcast service is a test service or a serviceautonomously used in the corresponding system and thus a broadcastreceiver can ignore the service or hide the same in a service list.

The SP_indicator information can indicate whether service protection isapplied to one or more components in the corresponding broadcastservice.

The num_component information can indicate the number of componentsconstituting the corresponding broadcast service.

The component_id information can be used as an identifier foridentifying the corresponding component in the broadcast service.

The DP_id information can be used as an identifier indicating a DPthrough which the corresponding component is transmitted.

The RoHC_init_descriptor can include information related to overheadreduction and/or header recovery. The RoHC_init_descriptor can includeinformation for identifying a header compression method used at atransmitting end.

FIG. 50 illustrates a broadcast system issuing an emergency alertaccording to an embodiment of the present invention.

Upon reception of information related to an emergency alert from analert authority/originator, a broadcasting station (transmitter)converts the information related to the emergency alert into emergencyalert signaling in a format adapted to a broadcast system or generatesemergency alert signaling including the information related to theemergency alert. In this case, the emergency alert signaling may includea common alerting protocol (CAP) message. The broadcasting station cantransmit the emergency alert signaling to a receiver. Here, thebroadcasting station can transmit the emergency alert signaling througha path through which normal broadcast data is delivered. Otherwise, thebroadcasting station may transmit the emergency alert signaling througha path different from the path through which normal broadcast data isdelivered. The emergency alert signaling may be generated in the form ofan emergency alert table (EAT) which will be described later.

The receiver receives the emergency alert signaling. An emergency alertsignaling decoder can parse the emergency alert signaling to obtain theCAP message. The receiver generates an emergency alert message usinginformation of the CAP message and displays the emergency alert message.

FIG. 51 illustrates a syntax of an emergency alert table (EAT) accordingto an embodiment of the present invention.

Information related to an emergency alert can be transmitted through anEAC. The EAC corresponds to the aforementioned dedicated channel

The EAT according to an embodiment of the present invention may includeEAT_protocol_version information, automatic_tuning_flag information,num_EAS_messages information, EAS_message_id information,EAS_IP_version_flag information, EAS_message_transfer_type information,EAS_message_encoding_type information, EAS_NRT_flag information,EAS_message_length information, EAS_message_byte information, IP_addressinformation, UDP_port_num information, DP_id information,automatic_tuning_channel_number information, automatic_tuning_DP_idinformation, automatic_tuning_service_id information and/orEAS_NRT_service_id information.

The EAT_protocol_version information indicates a protocol versioncorresponding to the received EAT.

The automatic_tuning_flag information indicates whether the receiverautomatically performs channel tuning.

The num_EAS_messages information indicates the number of messagesincluded in the EAT.

The EAS_message_id information identifies each EAS message.

The EAS_IP_version_flag information indicates IPv4 when theEAS_IP_version_flag information has a value of 0 and indicates IPv6 whenthe EAS_IP_version_flag information has a value of 1.

The EAS_message_transfer_type information indicates an EAS messagetransfer type. The EAS_message_transfer_type information indicates “notspecified” when the EAS_message_transfer_type information is 000,indicates “no alert message (only AV content)” when theEAS_message_transfer_type information is 001 and indicates that thecorresponding EAT includes an EAS message when theAS_message_transfer_type information is 010. To this end, a length fieldand a field with respect to the corresponding EAS message are added.When the EAS_message_transfer_type information is 011, this informationindicates that the corresponding EAS message is transmitted through adata pipe. The EAS can be transmitted in the form of an IP datagramwithin the data pipe. To this end. IP address information, UDP portinformation and DP information of a physical layer to which the EASmessage is transmitted may be added.

The EAS_message_encoding_type information indicates information aboutencoding type of an emergency alert message. For example, anEAS_message_encoding_type information value of 000 can indicate “notspecified”, an EAS_message_encoding_type information value of 001 canindicate “no encoding”, an EAS_message_encoding_type information valueof 010 can indicate DEFLATE algorithm (RFC1951) andEAS_message_encoding_type information values of 011 to 111 can bereserved for other encoding types.

The EAS_NRT_flag information indicates presence or absence of NRTcontent and/or NRT data related to a received message. An EAS_NRT_flaginformation value of 0 indicates absence of NRT content and/or NRT datarelated to a received emergency message, whereas and an EAS_NRT_flaginformation value of 1 indicates presence of NRT content and/or NRT datarelated to the received emergency message.

The EAS_message_length information indicates the length of an EASmessage.

The EAS_message_byte information includes content of the EAS message.

The IP_address information indicates the IP address of an IP packetcarrying the EAS message.

The UDP_port_num information indicates the number of a UDP port throughwhich the EAS message is transmitted.

The DP_id information identifies a data pipe through which the EASmessage is transmitted.

The automatic_tuning_channel_number information includes informationabout the number of a channel to be tuned to.

The automatic_tuning_DP_id information identifies a data pipe throughwhich corresponding content is transmitted.

The automatic_tuning_service_id information identifies a service towhich the corresponding content belongs.

The EAS_NRT_service_id information identifies an NRT servicecorresponding to a case in which NRT content and data related to areceived emergency alert message are transmitted, that is, when theEAS_NRT_flag is enabled.

FIG. 52 illustrates a method for identifying information related toheader compression, which is included in a payload of a link layerpacket according to an embodiment of the present invention.

When header compression is performed on a packet delivered from the linklayer to an upper layer, as described above, necessary information needsto be generated in a signaling form and transmitted to the receiver suchthat the receiver can recover the header of the packet. Such informationcan be referred to as header compression signaling information.

The header compression signaling information can be included in apayload of a link layer packet. In this case, the transmitter can embedidentification information for identifying the type of the headercompression signaling information, which is included in the payload ofthe link layer packet, in the header of the link layer packet or atransmission parameter (signaling information of the physical layer) ofthe physical layer and transmit the link layer packet header or thetransmission parameter including the identification information to thereceiver.

According to an embodiment, the identification information can indicatethat initialization information is included in the payload of the linklayer packet when the value thereof is 000 and indicate that aconfiguration parameter is included in the payload of the link layerpacket when the value thereof is 001. In addition, the identificationinformation can indicate that static chain information is included inthe payload of the link layer packet when the value thereof is 010 andindicate that dynamic chain information is included in the payload ofthe link layer packet when the value thereof is 011.

Here, the header compression signaling information may be called contextinformation. According to an embodiment, the static chain information orthe dynamic chain information may be called context information or boththe static chain information and the dynamic chain information may becalled context information.

FIG. 53 illustrates initialization information according to anembodiment of the present invention.

Initialization information included in a payload of a link layer packetmay include num_RoHC_channel information, max_cid information,large_cids information. num_profiles information, profile( ) element,num_IP_stream information and/or IP_address ( ) element.

The num_RoHC_channel information indicates the number of RoHC channels.

The max_cid information is used to indicate a maximum CID value to adecompressor.

The large_cid information has a Boolean value and indicates whether ashort CID (0˜15) or embedded CID (0˜16383) is used for a CIDconfiguration. Accordingly, bytes representing a CID are determined.

The num_profiles information indicates the number of RoHC profiles.

The profile( ) element includes information about a header compressionprotocol in RoHC. In RoHC, a stream can be compressed and recovered onlywhen the compressor and the decompressor have the same profile.

The num_IP_stream information indicates the number of IP streams.

The IP_address ( ) element includes the IP address of aheader-compressed IP packet.

FIG. 54 illustrates a configuration parameter according to an embodimentof the present invention.

A configuration parameter included in a link layer packet payload mayinclude RoHC_channel_id information, num_context information, context_idinformation, context_profile information, packet_configuration_modeinformation and/or context_transmission_mode information.

The RoHC_channel_id information identifies an RoHC channel.

The num_context information indicates the number of RoHC contexts.

The context_id information identifies an RoHC context. The context_idinformation can indicate a context to which the following RoHC relatedfield corresponds. The context_id information can correspond to acontext identifier (CID).

The context_profile information includes information about a headercompression protocol in RoHC. In RoHC, a stream can be compressed andrecovered only when the compressor and the decompressor have the sameprofile.

The packet_configuration_mode information identifies a packetconfiguration mode. Packet configuration modes have been describedabove.

The context_transmission_mode information identifies a contexttransmission mode. Context transmission modes have been described above.A context can be transmitted through a path through which normalbroadcast data is delivered or a path allocated for signalinginformation transmission.

FIG. 55 illustrates static chain information according to an embodimentof the present invention.

Static chain information included in a link layer packet payload mayinclude context_id information, context_profile information,static_chain_length information, static_chain ( ) element,dynamic_chain_incl information, dnamic_chain_length information and/or adynamic_chain ( ) element.

The context_id information identifies an RoHC context. The context_idinformation can indicate a context to which the following RoHC relatedfield corresponds. The context_id information can correspond to acontext identifier (CID).

The context_profile information includes information about a headercompression protocol in RoHC. In RoHC, a stream can be compressed andrecovered only when the compressor and the decompressor have the sameprofile.

The static_chain_length information indicates the length of thestatic_chain ( ) element.

The static_chain ( ) element includes information belonging to a staticchain extracted from an upper layer packet during RoHC headercompression.

The dynamic_chain_incl information indicates whether dynamic chaininformation is included.

The dynamic_chain_length information indicates the length of thedynamic_chain ( ) element.

The dynamic_chain ( ) element includes information belonging to adynamic chain extracted from the upper layer packet during RoHC headercompression.

FIG. 56 illustrates dynamic chain information according to an embodimentof the present invention.

Dynamic chain information included in a link layer packet payload mayinclude context_id information, context_profile information,dynamic_chain_length information and/or a dynamic_chain ( ) element.

The context_id information identifies an RoHC context. The context_idinformation can indicate a context to which the following RoHC relatedfield corresponds. The context_id information can correspond to acontext identifier (CID).

The context_profile information includes information about a headercompression protocol in RoHC. In RoHC, a stream can be compressed andrecovered only when the compressor and the decompressor have the sameprofile.

The dynamic_chain_length information indicates the length of thedynamic_chain ( ) element.

The dynamic_chain ( ) element includes information belonging to adynamic chain extracted from an upper layer packet during RoHC headercompression.

FIG. 57 illustrates header structures of a link layer packet accordingto other embodiments of the present invention.

Firstly, embodiment t57010 in which a single whole input packet isincluded and encapsulated in a link layer packet is described. This canbe called single packet encapsulation, as described above.

In this case (t57010), the header of the link layer packet can startwith the aforementioned Packet_Type field followed by the PC field.Here, the Packet_Type field can indicate the type of the input packetincluded in the link layer packet, as described above. The PC field canindicate a payload configuration of the link layer packet, as describedabove. The PC field can indicate whether a single whole packet isincluded in the payload or packets are concatenated and included in thepayload or a packet is segmented and included in the payload accordingto the value thereof. In one embodiment, a PC field value of 0 indicatesthat a single whole input packet is included in the payload of the linklayer packet. A PC field value of 1 indicates that segmented orconcatenated input packets are included in the payload of the link layerpacket.

The PC field can be followed by an HM field. The HM field can indicate aheader mode of the link layer packet, as described above. That is, theHM field can indicate whether the single input packet included in thelink layer packet is a short packet or a long packet, as describedabove. Accordingly, the header structure following the HM field can bechanged.

When the input packet is a short packet, that is, when the HM field hasa value of 0, an 11-bit length field can be present. This length fieldcan indicate the length of the payload of the link layer packet.

When the input packet is a long packet, that is, when the HM field has avalue of 1, the 11-bit length field can be followed by a 5-bitadditional length field. The 2-byte length field can indicate the lengthof the link layer payload. Here, the length field can be divided into abase header corresponding to the 11-bit length field and an additionalheader corresponding to the remaining 5-bit length field. The two lengthfields can be followed by a 2-bit reserved field and an LF field. Thereserved field corresponds to bits reserved for future use. The LF fieldis a flag indicating whether a label field follows the LF field. Thelabel field is a kind of sub stream label and can be used to filter aspecific upper layer packet stream at a link layer level, like a substream ID. An upper layer packet stream and sub stream label informationcan be mapped according to mapping information. The LF field cancorrespond to the aforementioned SIF field. The label field cancorrespond to the aforementioned SID field. Here, the label field may becalled an optional header. The label field may have a size of 3 bytesaccording to an embodiment.

Secondly, an embodiment t57020 in which one segment of an input packetis included and encapsulated in the link layer packet is described.Here, the segment may be generated by segmenting one input packet. Thiscase can be referred to as segmentation as described above.

The link layer header can start with the Packet_Type field and the PCfield. The PC field can be followed by an S/C field. The S/C field canindicate whether the link layer payload includes concatenated inputpackets or segments of a packet, as described above. The link layerheader structure can be changed according to whether the link layerpayload includes concatenated input packets or segments of a packet.

When the S/C field is 0, that is, when the link layer payload includessegments of a packet, the S/C field can be sequentially followed by asegment ID field and a segment sequence number field. When the linklayer packet includes segments other than the first segment, an LI fieldand/or the segment length ID field can be sequentially located. When thelink layer packet includes the first segment, a first segment lengthfield and/or an LF field can be located. That is, the link layer headerincluding the first segment may not include the LI field. Here, thefirst segment length field can directly indicate the length of the firstsegment included in the link layer packet. The LF field may or may notbe followed by the label field according to the value thereof, asdescribed above. Other fields are as described above.

Thirdly, an embodiment t57030 in which multiple input packets areconcatenated and encapsulated in the link layer packet is described.This case can be called concatenation.

The link layer header can start with the Packet_Type field and the PCfield. The PC field can be followed by the SiC field as in thesegmentation case. The S/C field can be followed by the aforementionedcount field and a length mode (LM) field. The count field may be a 2-bitfield and indicate that 2, 3, 4 and 5 input packets are concatenatedwhen having values of 00, 01, 10 and 11, respectively. Otherwise, a3-bit count field may be used, as described above.

The LM field can indicate whether short input packets are concatenatedand encapsulated or long input packets are concatenated andencapsulated. When short input packets are concatenated, the LM fieldhas a value of 0 and as many 11-bit length fields as the number of inputpackets may follow the LM field. When long input packets areconcatenated, the LM field has a value of 1 and as many 2-byte lengthfields as the number of input packets may follow the LM field. Here, aninput packet shorter than 2048 bytes can be classified as a short inputpacket and an input packet equal to or longer than 2048 bytes can beclassified as a long input packet.

Short input packets and long input packets may be mixed and concatenatedaccording to an embodiment. In this case, 11-bit length fields for theshort input fields and 2-byte length fields for the long input packetscan be mixed and located. These length fields can be positioned in theheader in the same order as the input packets corresponding thereto.

Some fields may be omitted from the aforementioned link layer packetheader structure according to an embodiment. In addition, some fieldsmay be changed or added and the order thereof may be changed.

FIG. 58 illustrates a syntax of the link layer packet header structureaccording to another embodiment of the present invention.

The syntax indicates the aforementioned link layer packet headerstructure according to another embodiment of the present invention. Asdescribed above, the Packet_Type field and the PC field can be commonlypositioned in the header structure.

When the PC field is 0, the header mode field is present. When theheader mode field is 0, a 11-bit length field can be provided. When theheader mode field is 1, a 2-byte length field, an LF field and reservedbits can be sequentially positioned. The label field may be additionallypresent according to the value of the LF field.

When the PC field is 1, the S/C field follows the PC field. When the S/Cfield is 0, the segment ID field and the segment sequence number fieldcan follow the S/C field. When the segment sequence number field is0000, that is, the first segment is included in the link layer packet,the first segment length field and the LF field can be positioned afterthe segment sequence number field. The label field may be additionallypresent according to the value of the LF field. When the segmentsequence number field has a value other than 0000, the LI field and thesegment length ID field can follow the same.

When the S/C field is 1, the count field and the LM field can follow theS/C field. As many length fields as the number indicated by the countfield can be present. An 11-bit length field can be provided for a shortinput packet and a 2-byte length field can be provided for a long inputpacket.

Padding bits can be positioned in the remaining part.

Some fields may be omitted from the aforementioned link layer packetheader structure according to an embodiment. In addition, some fieldsmay be changed or added and the order thereof may be changed.

FIG. 59 illustrates a case in which a single whole input packet isincluded in a link layer payload, in the link layer packet headerstructure according to another embodiment of the present invention.

A first embodiment t59010 corresponds to short single packet insulation.As described above, the Packet_Type field, the PC field and the HMfield, which are sequentially positioned, are followed by an 11-bitlength field. The link layer packet can have a total header length of 2bytes and the header can be followed by a link layer payload. Here, thePC field and the HM field can respectively have values of 0 and 0.

A second embodiment t59020 corresponds to long single packetencapsulation. As described above, the Packet_Type field, the PC fieldand the HM field, which are sequentially positioned, are followed by a2-byte length field. The 2-byte length field may include an 11-bitlength field and an additional 5-bit length field, as described above.These length fields may refer to an LSB part and an MSB part. The lengthfield can be followed by reserved bits and the LF field. The link layerpacket can have a total header length of 3 bytes and the header can befollowed by a link layer payload. Here, the PC field, the HM field andthe LF field can respectively have values of 0, 1 and 0.

A third embodiment 159030 corresponds to a case in which a long singlepacket is encapsulated and the label field is additionally included inthe header structure. While the third embodiment corresponds to theaforementioned long single packet encapsulation case, the LF field is 1and can be followed by the label field.

FIG. 60 illustrates a case in which one segment obtained by segmentingan input packet is included in a link layer payload in the link layerpacket header structure according to another embodiment of the presentinvention.

A first embodiment t60010 corresponds to a link layer packet structureincluding the first segment from among segments of the input packet. Asdescribed above, the Packet_Type field, the PC field and the S/C field,which are sequentially positioned, are followed by the length ID fieldand the segment sequence number field. Here, the PC field, the S/C fieldand the segment sequence number field can be 0, 0 and 0000,respectively. The first segment length field can be positioned in theheader structure since the first segment is included in the link layerpacket. The first segment length field can directly indicate the lengthof the first segment, as described above. The first segment length fieldcan be followed by the LF field.

A second embodiment t60020 corresponds to a link layer packet structureincluding a segment other than the first or last segment from among thesegments of the input packet. As described above, the Packet-Type field,the PC field and the S/C field, which are sequentially positioned, canbe followed by the length ID field and the segment sequence numberfield. Here, the PC field and the S/C field can be 0 and 0,respectively. The LI field is positioned in the header structure sincethe first segment is not included in the link layer packet, and the LIfield can be 0 since the last segment is not included in the link layerpacket. The segment length ID field can follow the LI field.

A third embodiment t60030 corresponds to a link layer packet structureincluding the last segment from among the segments of the input packet.As described above, the Packet_Type field, the PC field and the SiCfield, which are sequentially positioned, can be followed by the lengthID field and the segment sequence number field. Here, the PC field andthe S/C field can be 0 and 0, respectively. The LI field is positionedin the header structure since the first segment is not included in thelink layer packet, and the LI field can be 1 since the last segment isincluded in the link layer packet. The segment length ID field canfollow the LI field.

A fourth embodiment t60040 corresponds to a link layer packet structurein which the first segment from among the segments of the input packetand the LF field is 1. While the fourth embodiment corresponds to thefirst embodiment, the label field may be added according to the value ofthe LF field.

FIG. 61 is a table showing a case in which one segment of an inputpacket is included in a link layer payload in the link layer packetheader structure according to another embodiment of the presentinvention.

It is assumed that one input packet is segmented into 8 segments. Alllink layer packets including the segments have the same Packet_Typefield value since the segments have been derived from one input packet.The PC field and the S/C field are 1 and 0, respectively, as describedabove. The link layer packets have the same segment ID field value sincethe segments have been derived from one input packet. The segmentsequence number field can indicate the order of the segments. A 3-bitsegment sequence number field may be used according to an embodiment.

A link layer packet having the first segment includes the first segmentlength field so as to indicate the length of the payload thereof. Inthis case, the LI field and the segment length ID field may not bepresent.

Link layer packets having segments other than the first segment caninclude the LI field and the segment length ID field without having thelength field which directly indicates the payload length. The segmentlength ID field can select one of the aforementioned designated lengthIDs and indicate the length of the corresponding segment according tothe selected value. The LI field can be 0 when the corresponding segmentis not the last segment and 1 when the corresponding segment is the lastsegment.

FIG. 62 illustrates a case in which multiple input packets areconcatenated and included in link layer payloads in the link layerpacket header structure according to another embodiment of the presentinvention.

A first embodiment t62010 illustrates a case in which short inputpackets are concatenated and included in link layer payloads. ThePacket_Type field, the PC field and the S/C field are sequentiallypositioned and followed by the count field and the LM field. The PCfield, the S/C field and the LM field can be 1, 1 and 0, respectively,according to the aforementioned definition.

11-bit length fields can be sequentially positioned following theaforementioned fields. The length fields respectively indicating thelengths of the concatenated short input packets can be arranged in thesame order as the input packets corresponding thereto. After the lastlength field, the remaining part can be filled with padding bits Pcorresponding to 8 bits. Subsequently, the concatenated input packetscan be arranged.

A second embodiment t62020 illustrates a case in which long inputpackets are concatenated and included in link layer payloads. ThePacket_Type field, the PC field and the S/C field are sequentiallypositioned and followed by the count field and the LM field. The PCfield, the S/C field and the LM field can be 1, 1 and 1, respectively,according to the aforementioned definition.

2-bytes length fields can be sequentially positioned following theaforementioned fields. The length fields respectively indicating thelengths of the concatenated long input packets can be arranged in thesame order as the input packets corresponding thereto. Subsequently, theconcatenated input packets can be arranged.

FIG. 63 illustrates a case in which a single whole input packet isincluded in a link layer payload in the link layer packet headerstructure according to another embodiment of the present invention.

First and second embodiments t63010 and t63020 can correspond to theaforementioned link layer packet header structure with respect to singlepacket encapsulation. However, a 2-byte length field is included in theheader structure in the first embodiment and an 11-bit additional lengthfield is included in the header structure in the second embodiment, fora case in which a long input packet is included in the link layerpacket. In this case, the length fields can respectively refer to an LSBpart and an MSB part which indicate lengths. The 2-byte length field canbe followed by reserved bits. The last bit can be used as the LF field,as described above.

A third embodiment t63030 is similar to the aforementioned link layerpacket header structure with respect to single packet encapsulation. Thelink layer packet header structure when a short input packet is includedin the link layer packet payload corresponds to the aforementioned linklayer packet header structure with respect to single packetencapsulation. When a long input packet is included in the link layerpayload, a length extension field can replace the 5-bit additionallength field.

The length extension field indicates extension of a length field. Thenumber of bits occupied by the length extension field can be changedaccording to packet structure. It is assumed that the length extensionfield is 2 bits in the present embodiment for convenience ofdescription. For example, when the length extension field is not used,that is, when HM=0, this indicates that a short input packet isencapsulated, and the 11-bit length field can indicate a payload lengthin the range of 0 to 2047 bytes. When the length extension field isused, the value of the length extension field can function as an offsetin indication of the payload length. When the length extension field is00, the 11-bit length field indicates a payload in the range of 2048 to4095 bytes. When the length extension field is 01, 10 and 11, the 11-bitlength field respectively indicates payload lengths in the ranges of4096 to 6143 bytes, 6144 to 8191 bytes and 8192 to 10239 bytes. Forexample, when the 11-bit length field has a value indicating a “1-bytepayload length” and the length extension field is 00, this indicates apayload length of 2049 bytes. If the 11-bit length field has a valueindicating a “1-byte payload length” and the length extension field is01, this indicates a payload length of 4097 bytes. In this manner, thepayload length can be indicated even in the case of long single packetencapsulation.

A fourth embodiment t63040 corresponds to the aforementioned link layerheader structure with respect to single packet encapsulation. The 2-bytelength field can be replaced by the 11-bit length field and theadditional 5-bit length field. In this case, the length fields canrespectively refer to an LSB part and an MSB part. The label field maybe added according to the value of the LF field value. The position ofthe label field can be changed according to embodiments.

FIG. 64 is a table showing header lengths in the link layer packetheader structure according to another embodiment of the presentinvention.

When a short single input packet is encapsulated, the PC field and theHM field can have a value of 0. The total header length can be 2 bytesaccording to the 11-bit length field. In the table. x indicates that thecorresponding bit can be any value. For example, the 11-bit length fieldis represented by 11 xs (xxxxxxxxxxx) since the 11-bit length field isdetermined by the payload length and thus is irrelevant to the headerlength.

When a long single input packet is encapsulated, the PC field and the HMfield can respectively have values of 0 and 1. Subsequently, the 11-bitlength field and the 5-bit additional length field are added and thusthe total header length can be 3 bytes.

In a segmentation case, the PC field and the S/C field of each linklayer packet can be 1 and 0, respectively. A link layer packet includingthe first segment can have a segment sequence number field of 0000. Inthe present embodiment, the LF field can be 0. In this case, the totalheader length can be 3 bytes. A link layer packet including a segmentother than the first segment can have a 4-bit segment sequence numberfield followed by an LI field. In this case, the total header length canbe 2 bytes.

When short input packets are concatenated, the PC field and the S/Cfield can be 1. The count field can indicate that n packets have beenencapsulated. In this case, the LM field can be 0. The total headerlength can be represented by (11n/8+1) bytes since n 11-bit lengthfields are used and 1 byte is used for the front part of the header.However. P padding bits may need to be added for byte alignment. In thiscase, the header length can be represented by ((11n+P)/8+1) bytes.

When long input packets are concatenated, the PC field and the S/C fieldcan be 1. The count field can indicate that n packets have beenencapsulated. In this case, the LM field can be 1. The total headerlength can be represented by (2n+1) bytes since n 2-byte length fieldsare used and 1 byte is used for the front part of the header.

FIG. 65 illustrates a case in which one segment of an input packet isincluded in a link layer payload in the link layer packet headerstructure according to another embodiment of the present invention.

The illustrated embodiment t65010 corresponds to the aforementioned linklayer packet header structure with respect to segmentation according toanother embodiment of the present invention. The Packet_Type field, thePC field and the S/C field are sequentially arranged and followed by thesegment ID field and the segment sequence number field. The PC field andthe S/C field can be 1 and 0, respectively. When the link layer packethas the first segment, the link layer packet can include the firstsegment length field. 1 bit following the first segment length field maybe a reserved bit or may be assigned to the LF field, as describedabove. When the link layer packet has a segment other than the firstsegment, the link layer packet can include the LI field and the segmentlength ID field.

In table t65020 showing the above embodiment, the Packet_Type field canhave the same value, the PC field can be 1 and the S/C field can be 0,for a total of 5 segments. The segment ID field can have the same value.The segment sequence number field can indicate sequence numbers of thesegments. In the case of the first segment, the first segment lengthfield indicates the length thereof and the LI field may not be present.In the case of a segment other than the first segment, the length isindicated using the segment length ID field and the LI field can be 0 or1 according to whether or not the segment is the last segment.

FIG. 66 illustrates a case in which one segment of an input packet isincluded in a link layer payload in the link layer packet headerstructure according to another embodiment of the present invention.

The illustrated embodiment t66010 is similar to the aforementioned linklayer packet header structure with respect to segmentation according toanother embodiment of the present invention. However, the headerstructure can be changed in the case of link layer packets havingsegments other than the first segment. In this case, the LI field can befollowed by the segment length field instead of the segment length IDfield. The segment length field can directly indicate the length of thesegment included in the corresponding link layer packet. According to anembodiment, the segment length field may have a length of 11 bits. Inthis case, the first segment length field may be called a segment lengthfield.

In table t66020 showing the above embodiment, the Packet_Type field canhave the same value, the PC field can be 1 and the S/C field can be 0,for a total of 5 segments. The segment ID field can have the same value.The segment sequence number field can indicate sequence numbers of thesegments. The length of the link layer payload can be indicated by thesegment length field irrespective of whether the corresponding segmentis the first segment. The LI field is not present when the correspondinglink layer packet includes the first segment, whereas the LI field ispresent when the corresponding link layer packet includes a segmentother than the first segment. The LI field can be 0 or 1 according towhether or not the corresponding segment is the last segment.

FIG. 67 illustrates a case in which one segment of an input packet isincluded in a link layer payload in the link layer packet headerstructure according to another embodiment of the present invention.

The illustrated embodiment t67010 is similar to the aforementioned linklayer packet header structure with respect to segmentation according toanother embodiment of the present invention. However, the headerstructure can be changed in the case of link layer packets havingsegments other than the first segment. In this case, the LI field canfollow the segment length field. The segment length field is asdescribed above, and the first segment length field may also be called asegment length field.

In table t67020 showing the above embodiment, the Packet_Type field canhave the same value, the PC field can be 1 and the S/C field can be 0,for a total of 5 segments. The segment ID field can have the same value.The segment sequence number field can indicate sequence numbers of thesegments. The length of the link layer payload can be indicated by thesegment length field irrespective of whether the corresponding segmentis the first segment. The LI field is not present when the correspondinglink layer packet includes the first segment, whereas the LI field ispresent when the corresponding link layer packet includes a segmentother than the first segment. The LI field can be 0 or 1 according towhether or not the corresponding segment is the last segment.

FIG. 68 illustrates a case in which one segment of an input packet isincluded in a link layer payload in the link layer packet headerstructure according to another embodiment of the present invention.

The illustrated embodiment t68010 is similar to the aforementioned linklayer packet header structure with respect to segmentation according toanother embodiment of the present invention. In this case, however, acommon header structure can be used irrespective of whether thecorresponding segment is the first segment. The Packet_Type field to thesegment sequence number fields have the same structures as theabove-described structures. The segment sequence number field can befollowed by the LI field irrespective of whether or not thecorresponding segment is the first segment, and the LI field can befollowed by the segment length field which indicates the payload lengthof the corresponding link layer packet. The segment length field is asdescribed above. In the present embodiment, the segment ID field can beomitted and the segment length field can follow the S/C field. The LIfield can be followed by the aforementioned SIF field.

In table t68020 showing the above embodiment, the Packet_Type field canhave the same value, the PC field can be 1 and the S/C field can be 0,for a total of 5 segments. The segment ID field can have the same value.The segment sequence number field can indicate sequence numbers of thesegments. The LI field is present irrespective of whether or not thecorresponding segment is the first segment. The LI field can be 0 or 1according to whether or not the corresponding segment is the lastsegment. The length of the link layer payload can be indicated by thesegment length field irrespective of whether the corresponding segmentis the first segment.

FIG. 69 illustrates a case in which multiple input packets areconcatenated and included in a link layer payload in the link layerpacket header structure according to another embodiment of the presentinvention.

The illustrated embodiment t69010 may correspond to the aforementionedlink layer packet header structure with respect to concatenationaccording to another embodiment of the present invention. ThePacket_Type field, the PC field and the S/C field can be sequentiallyarranged and followed by the count field and the LM field. The PC fieldand the S/C field can be 1. When short packets are concatenated andencapsulated, as many 11-bit length fields as the number of concatenatedpackets can be present according to the value of the LM field. When longpackets are concatenated and encapsulated, as many 2-byte length fieldsas the number of concatenated packets can be present.

The present embodiment can be represented by table t69020 on the basisof the number of concatenated input packets. When the link layer packethas the first segment, the link layer packet can include the firstsegment length field. 1 bit following the first segment length field maybe a reserved bit or may be assigned to the LF field, as describedabove. When the link layer packet has a segment other than the firstsegment, the link layer packet can include the LI field and the segmentlength ID field. A count field value of 00 indicates that 2 inputpackets have been concatenated. In this case, 2 length fields, that is,22 bits are used, and 2 padding bits can be used for byte alignments.Accordingly, the total header length can be 4 bytes and a header portionper input packet can be 2 bytes.

Count field values of 01, 10 and 11 respectively indicate that 3, 4 and5 input packets have been concatenated. In this case, 3, 4 and 5 lengthfields, that is, 33, 44 and 55 bits are respectively used for therespective cases and 7, 4 and 1 padding bits can be used for bytealignment in the respective cases. Accordingly, the total header lengthscan be 6, 7 and 8 bytes and a header portion per input packet can be2.0, 1.75 and 1.60 bytes in the respective cases.

FIG. 70 illustrates a case in which multiple input packets areconcatenated and included in a link layer payload in the link layerpacket header structure according to another embodiment of the presentinvention.

The illustrated embodiments t70010 and t70020 may correspond to theaforementioned link layer packet header structure with respect toconcatenation according to another embodiment of the present invention.In this case, however, the LM field can be omitted from theaforementioned header structure. The Packet_Type field, the PC field andthe S/C field can be sequentially arranged and followed by the countfield. The PC field and the S/C field can be 1.

In the illustrated embodiment t70010, as many 11-bit length fields asthe number of concatenated packets can be present. Here, the length of ashort input packet, which can be represented by 11 bits, is indicated bythe 11-bit length field. In the case of an input packet longer than 11bits, the aforementioned single packet encapsulation or segment can beused instead of concatenation. The link layer header structure of thepresent embodiment can be used when whether concatenation or singlepacket encapsulation/segmentation is used has been designated on thebasis of the size that can be represented by 11 bits.

In the illustrated embodiment t70020, as many 2-byte length fields asthe number of concatenated packets can be present. The link layer headerstructure of the present embodiment supports concatenation for allpackets having lengths which can be represented by 2 bytes.

The above embodiments can be represented by tables t70030 and t70040 onthe basis of the number of concatenated input packets. Description ofthe tables has been given above.

In table t70030 with respect to the embodiment t70010, when the countfield is 000, for example, 2 input packets have been concatenated, 2length fields, that is, 22 bits are used, and 2 padding bits are usedfor byte alignment. Accordingly, the total header length can be 4 bytesand a header portion per input packet can be 2 bytes. When the countfield is 001, 3 input packets have been concatenated, 3 length fields,that is, 33 bits are used, and 7 padding bits are used for bytealignment. Accordingly, the total header length can be 6 bytes and aheader portion per input packet can be 2 bytes.

In table t70040 with respect to embodiment t70020, when the count fieldis 000, for example, 2 input packets have been concatenated, and 2length fields, that is, 4 bytes can be used. Accordingly, the totalheader length can be 5 bytes and a header portion per input packet canbe 2.50 bytes. When the count field is 001, 3 input packets have beenconcatenated, and 3 length fields, that is, 6 bytes can be used.Accordingly, the total header length can be 7 bytes and a header portionper input packet can be 2.33 bytes. In this case, padding bits may notbe needed.

FIG. 71 illustrates a link layer packet structure when word based lengthindication is used according to another embodiment of the presentinvention.

When a packet of an upper layer is generated on a word basis, a lengthfield can indicate a length on a word basis instead of a byte basis.That is, when an input packet has a length of 4 bytes, the link layerheader can be further optimized because the sizes of the aforementionedlength fields can be reduced when a length is indicated on a word basis.

When a length is indicated on a word basis, the link layer headerstructure is similar to the aforementioned link layer packet headerstructure according to another embodiment of the present invention. Thepositions, configurations and operations of the respective fields are asdescribed above. However, the sizes of the fields are reduced.

In single packet encapsulation (t71010), the field indicating thepayload length can be reduced by 2 bits. That is, the 11-bit lengthfield can be reduced to 9 bits and 2 bits can be reserved for futureuse. In addition, when a long input packet is used, the 16-bit lengthfield can be reduced to 14 bits. That is, bits corresponding to thelength field used as an MSB can be reduced. An input packet length of upto 2044 bytes (511 words) can be indicated using a 9-bit length fieldand an input packet length of up to 64 kbytes (65532 bytes, 16383 words)can be indicated using a 14-bit length field. The 2 bits can be reservedfor future use. The reserved bits may be used as an indicator (HEFfield) indicating presence or absence of the aforementioned optionalheader.

In the case of segmentation or concatenation (t71020 and t71030), thelength fields can be optimized similarly. The 11-bit segment lengthfield and the first segment length field can be reduced to 9 bits. Inaddition, the 11-bit length fields and 2-byte length fields indicatingthe lengths of segments can be reduced to 9 bits and 14 bits,respectively. In this case, padding bits may be added for bytealignment.

This optimization method can be applied to all link layer packetstructures described in the present invention.

FIG. 72 is a table showing a link layer packet header structure whenword based length indication is used according to another embodiment ofthe present invention on the basis of the number of input packets.

The first table t72010 shows a case in which short input packets areconcatenated. When the count field is 00, 2 input packets have beenconcatenated, 2 length fields, that is, 18 bits, can be used and 6padding bits can be used for byte alignment. Accordingly, the totalheader length can be 4 bytes and a header portion per input packet canbe 2.0 bytes.

Count field values of 01, 10 and 11 respectively indicate that 3, 4 and5 input packets have been concatenated. In this case, 3, 4 and 5 lengthfields, that is, 27, 36 and 45 bits can be used and 5, 4 and 3 paddingbits can be used for byte alignment for the respective cases.Accordingly, the total header length can be 5, 6 and 7 bytes and aheader portion per input packet can be 1.67, 1.50 and 1.40 bytes in therespective cases.

The second table t72020 shows a case in which long input packets areconcatenated. When the count field is 00, 2 input packets have beenconcatenated, 2 length fields, that is, 28 bits, can be used and 4padding bits can be used for byte alignment. Accordingly, the totalheader length can be 5 bytes and a header portion per input packet canbe 2.50 bytes. When word based length indication is used, padding bitsmay be needed even when long input packets are concatenated.

Count field values of 01, 10 and 11 respectively indicate that 3, 4 and5 input packets have been concatenated. In this case, 3, 4 and 5 lengthfields, that is, 42, 56 and 70 bits can be used and 6, 0 and 2 paddingbits can be used for byte alignment for the respective cases.Accordingly, the total header length can be 7, 8 and 10 bytes and aheader portion per input packet can be 2.33, 2.00 and 2.00 bytes in therespective cases.

FIG. 73 illustrates a method for transmitting a broadcast signalaccording to an embodiment of the present invention.

The method for transmitting a broadcast signal according to anembodiment of the present invention may include the steps of generatinga plurality of input packets including broadcast data, generating a linklayer packet using the input packets, generating a broadcast signaland/or transmitting the broadcast signal.

Specifically, a first module at a service provider may generate aplurality of input packets (t73010). Here, the plurality of inputpackets may be MPEG2-TS packets, IP packets, packets in a specificformat, or packets to be defined and used in the future. The firstmodule may be a specific module that generates broadcast data and formsthe broadcast data in the form of input packets.

A second module at the service provider may generate at least one linklayer packet using the plurality of input packets (t73020). This stepmay include the aforementioned process of encapsulating input packets togenerate a link layer packet in the link layer. Here, the link layerpacket may have the packet structures according to the aboveembodiments.

In the present embodiment, the header of the link layer packet mayinclude packet type information and payload configuration information.The packet type information and payload configuration information may beincluded in the base header of the header of the link layer packet. Thepacket type information can indicate the type of input packets includedin the payload of the link layer packet, and the payload configurationinformation can indicate the configuration of the payload of the linklayer packet. The packet type information can correspond to theaforementioned Packet_Type field and the payload configurationinformation can correspond to the aforementioned PC field.

A third module at the service provider may generate a broadcast signalusing the generated link layer packet (t73030). This operation cancorrespond to operations, such as interleaving and framing, performed inthe physical layer using the link layer packet. A fourth module at theservice provider may transmit the generated broadcast signal (t73040).Here, the fourth module may correspond to an antenna.

In a method for transmitting a broadcast signal according to anotherembodiment of the present invention, the base header may further includefirst length information which indicates the length of the payload. Thefirst length information may correspond to the aforementioned length(LSB) field.

In a method for transmitting a broadcast signal according to anotherembodiment of the present invention, the payload may include a singleinput packet from among the input packets. That is, the link layerpacket can include a single input packet, as described above. When thelink layer packet includes a single input packet, the base header mayfurther include header mode information which indicates whether theheader of the link layer packet further includes an additional header.The header mode information can correspond to the aforementioned HMfield.

In a method for transmitting a broadcast signal according to anotherembodiment of the present invention, the additional header may furtherinclude second length information. The second length information may beconnected with the first length information to indicate the total lengthof the payload including the single input packet. Here, the secondlength information can correspond to the aforementioned length MSBfield. The present embodiment may correspond to a case in which a singlepacket is encapsulated.

In a method for transmitting a broadcast signal according to anotherembodiment of the present invention, the additional header may furtherinclude sub stream flag information which indicates whether the linklayer packet includes sub stream ID information. The sub stream IDinformation can correspond to the aforementioned SID information and thesub stream flag information can correspond to the aforementioned SIFinformation. The SID information can correspond to the aforementionedlabel information. The SIF information can correspond to theaforementioned LF field.

In a method for transmitting a broadcast signal according to anotherembodiment of the present invention, the payload may include a pluralityof input packets or segments of one input packet. That is, when a singlepacket is not included in the link layer packet (PC=1), the link layerpayload can include segments of an input packet or concatenated inputpackets. In this case, the base header may further include informationindicating whether the payload includes a plurality of input packets orsegments of an input packet. This information can correspond to theaforementioned S/C field.

In a method for transmitting a broadcast signal according to anotherembodiment of the present invention, the step of generating the linklayer packet may further include the steps of compressing the headers ofthe input packets, extracting context information from at least onecompressed input packet and encapsulating the context information andthe compressed input packets to generate link layer packets. The step ofextracting the context information may be a process of extracting staticchain information and/or dynamic chain information from input packetswhich are being compressed/have been compressed. After this process, thecontext information can be encapsulated in the link layer packets andthe input packets can also be encapsulated in the link layer packets.This operation may be performed by the aforementioned second module orsub-modules in the second module.

In a method for transmitting a broadcast signal according to anotherembodiment of the present invention, the link layer packets includingthe context information may be transmitted separately from thecompressed input packets. In a method for transmitting a broadcastsignal according to another embodiment of the present invention, thelink layer packets including the context information may be transmittedthrough a physical path for signaling. The context information may beseparately transmitted such that the context information can be receivedat the link layer level. The context information can be transmittedthrough a specific channel or PLP. Alternatively, the contextinformation may be transmitted through a normal physical path and thepath may be signaled.

In a method for transmitting a broadcast signal according to anotherembodiment of the present invention, an input packet may be one of anInternet protocol (IP) packet, a compressed IP packet and a transportstream (TS) packet. In addition, the input packet may be data of varioustypes/protocols indicated by the packet type field and/or Ethernetfield.

A description will be given of a method for receiving a broadcast signalaccording to an embodiment of the present invention, which is not shown.

The description will be given of a method for receiving a broadcastsignal according to an embodiment of the present invention may includethe steps of receiving a broadcast signal, acquiring a link layer packetof the broadcast signal and/or generating an output packet using thelink layer packet.

Specifically, a first module at a receiver may receive a broadcastsignal. The broadcast signal may be the broadcast signal transmittedfrom the service provider according to the aforementioned embodiment.The first module may be a reception device such as an antenna or atuner.

A second module at the receiver may acquire a link layer packet usingthe received broadcast signal. The link layer packet may be as describedabove. This process may correspond to a process of processing abroadcast signal in the physical layer at the receiver to output anoutput stream to the link layer.

Subsequently, a third module at the receiver may generate an outputpacket by processing the link layer packet. Here, the output packet maycorrespond to the input packet transmitted from the service provider tothe link layer. In this process, packets encapsulated in the link layerpacket can be recovered. This process can correspond to a reverseprocess of the aforementioned “step of generating a link layer packetusing input packets”.

Methods for receiving a broadcast signal according to embodiments of thepresent invention can correspond to the methods for transmitting abroadcast signal according the aforementioned embodiments of the presentinvention. The methods for receiving a broadcast signal can be performedby hardware modules (e.g., first, second, third and fourth modules)corresponding to the modules used in the methods for transmitting abroadcast signal. The methods for receiving a broadcast signal may haveembodiments corresponding to the embodiments of the aforementionedmethods for transmitting a broadcast signal.

The aforementioned steps may be omitted or replaced by other steps ofperforming similar/identical operations according to embodiments.

FIG. 74 illustrates an apparatus for transmitting a broadcast signalaccording to an embodiment of the present invention.

The apparatus for transmitting a broadcast signal according to anembodiment of the present invention may include the aforementioned firstmode, second module, third module and/or fourth module. Respectiveblocks and modules are as described above.

The apparatus for transmitting a broadcast signal and internalmodules/blocks thereof according to an embodiment of the presentinvention can perform the aforementioned embodiments of the method fortransmitting a broadcast signal according to the present invention.

A description will be given of an apparatus for receiving a broadcastsignal according to an embodiment of the present invention, which is notshown.

The apparatus for receiving a broadcast signal according to anembodiment of the present invention may include the aforementioned firstmodule, second module and/or third module at the receiver. Respectiveblocks and modules are as described above.

The apparatus for receiving a broadcast signal and internalmodules/blocks thereof according to an embodiment of the presentinvention can perform the aforementioned embodiments of the method forreceiving a broadcast signal according to the present invention.

The aforementioned internal blocks/modules of the apparatus may beprocessors executing consecutive processes stored in a memory and may behardware elements located inside/outside of the apparatus according toan embodiment.

The aforementioned modules may be omitted or replaced by other modulesperforming similar/identical operations according to embodiments.

Modules or units may be processors executing consecutive processesstored in a memory (or a storage unit). The steps described in theaforementioned embodiments can be performed by hardware/processors.Modules/blocks/units described in the above embodiments can operate ashardware/processors. The methods proposed by the present invention canbe executed as code. Such code can be written on a processor-readablestorage medium and thus can be read by a processor provided by anapparatus.

While the embodiments have been described with reference to respectivedrawings for convenience, embodiments may be combined to implement a newembodiment. In addition, designing a computer-readable recording mediumstoring programs for implementing the aforementioned embodiments iswithin the scope of the present invention.

The apparatus and method according to the present invention are notlimited to the configurations and methods of the above-describedembodiments and all or some of the embodiments may be selectivelycombined to obtain various modifications.

The methods proposed by the present invention may be implemented asprocessor-readable code stored in a processor-readable recording mediumincluded in a network device. The processor-readable recording mediumincludes all kinds of recording media storing data readable by aprocessor. Examples of the processor-readable recording medium include aROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical datastorage device and the like, and implementation as carrier waves such astransmission over the Internet. In addition, the processor-readablerecording medium may be distributed to computer systems connectedthrough a network, stored and executed as code readable in a distributedmanner.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims. Such modifications should notbe individually understood from the technical spirit or prospect of thepresent invention.

Both apparatus and method inventions are mentioned in this specificationand descriptions of both the apparatus and method inventions may becomplementarily applied to each other.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. Therefore, the scope of the invention should bedetermined by the appended claims and their legal equivalents, not bythe above description, and all changes coming within the meaning andequivalency range of the appended claims are intended to be embracedtherein.

In the specification, both the apparatus invention and the methodinvention are mentioned and description of both the apparatus inventionand the method invention can be applied complementarily.

[Mode for Invention]

Various embodiments have been described in the best mode for carryingout the invention.

INDUSTRIAL APPLICABILITY

The present invention is applied to broadcast signal providing fields.

Various equivalent modifications are possible within the spirit andscope of the present invention, as those skilled in the relevant artwill recognize and appreciate. Accordingly, it is intended that thepresent invention cover the modifications and variations of thisinvention provided they come within the scope of the appended claims andtheir equivalents.

The invention claimed is:
 1. A method for transmitting broadcastsignals, the method comprising: encapsulating input packets includingInternet Protocol (IP) packets or Transport Stream (TS) packets intolink layer packets in a link layer, each header of the link layerpackets including a base header having packet type information andpayload configuration information, the packet type informationrepresenting a type of the input packets in a payload of each link layerpacket, the payload configuration information representing aconfiguration of the payload of each link layer packet, wherein, for afirst link layer packet of the link layer packets including a singlepacket in a payload of the first link layer packet and an additionalheader following a base header of the first link layer packet, payloadconfiguration information of the base header of the first link layerpacket includes a first value and header mode information of the baseheader of the first link layer packet includes a second value, for asecond link layer packet of the link layer packets including a segmentedpacket in a payload in the second link layer packet and an additionalheader following a base header of the second link layer packet, payloadconfiguration information of the base header of the second link layerpacket includes a third value and S/C (segmentation/concatenation)information of the base header of the second link layer packet includesa fourth value, for a third link layer packet of the link layer packetsincluding a concatenated packet in a payload in the third link layerpacket and an additional header following a base header of the thirdlink layer packet, payload configuration information of the base headerof the third link layer packet includes the third value and S/Cinformation of the base header of the third link layer packet includes afifth value, and for at least one of the first link layer packet, thesecond link layer packet or the third link layer packet including anoptional header following the additional header of the at least one ofthe first link layer packet, the second link layer packet or the thirdlink layer packet, a flag of the additional header includes a sixthvalue; encapsulating the link layer packets including the first linklayer packet, the second link layer packet, and the third link layerpacket into data packets carried by a Data Pipe (DP) in a physicallayer; and transmitting a broadcast signal including the data packets.2. The method according to claim 1, wherein each header of the linklayer packets further includes first length information indicating alength of the payload.
 3. The method according to claim 2, wherein theadditional header further includes second length information, andwherein the second length information is connected with the first lengthinformation so as to indicate the total length of the payload includingthe single packet.
 4. The method according to claim 1, wherein the linklayer packets are generated by: compressing headers of at least oneinput packet; extracting context information from the at least one inputpacket having the compressed headers; and generating the link layerpackets by encapsulating the context information and the at least oneinput packet having the compressed headers.
 5. The method according toclaim 4, wherein the link layer packets including the contextinformation are transmitted separately from the at least one inputpacket having the compressed headers.
 6. The method according to claim4, wherein the link layer packets including the context information aretransmitted through a physical path for signaling.
 7. An apparatus fortransmitting broadcast signals, the apparatus comprising: anencapsulator configured to encapsulate input packets including InternetProtocol (IP) packets or Transport Stream (TS) packets into link layerpackets in a link layer, each header of the link layer packets includinga base header having packet type information and payload configurationinformation, the packet type information representing a type of theinput packets in a payload of each link layer packet, the payloadconfiguration information representing a configuration of the payload ofeach link layer packet, wherein, for a first link layer packet of thelink layer packets including a single packet in a payload of the firstlink layer packet and an additional header following a base header ofthe first link layer packet, payload configuration information of thebase header of the first link layer packet includes a first value andheader mode information of the base header of the first link layerpacket includes a second value, for a second link layer packet of thelink layer packets including a segmented packet in a payload in thesecond link layer packet and an additional header following a baseheader of the second link layer packet, payload configurationinformation of the base header of the second link layer packet includesa third value and S/C (segmentation/concatenation) information of thebase header of the second link layer packet includes a fourth value, fora third link layer packet of the link layer packets including aconcatenated packet in a payload in the third link layer packet and anadditional header following a base header of the third link layerpacket, payload configuration information of the base header of thethird link layer packet includes the third value and S/C information ofthe base header of the third link layer packet includes a fifth value,and for at least one of the first link layer packet, the second linklayer packet or the third link layer packet including an optional headerfollowing the additional header of the at least one of the first linklayer packet, the second link layer packet or the third link layerpacket, a flag of the additional header includes a sixth value; anencapsulator configured to encapsulate the link layer packets includingthe first link layer packet, the second link layer packet, and the thirdlink layer packet into data packets carried by a Data Pipe (DP) in aphysical layer; and a transmitter configured to transmit a broadcastsignal including the data packets.
 8. The apparatus according to claim7, wherein each header of the link layer packets further includes firstlength information indicating a length of the payload.
 9. The apparatusaccording to claim 8, wherein the additional header further includessecond length information, and wherein the second length information isconnected with the first length information so as to indicate the totallength of the payload including the single packet.
 10. The apparatusaccording to claim 7, wherein the encapsulator compresses headers of atleast one input packet, extracts context information from the at leastone input packet having the compressed headers, and generates the linklayer packets by encapsulating the context information and the at leastone input packet having the compressed headers.
 11. The apparatusaccording to claim 10, wherein the link layer packets including thecontext information are transmitted separately from the at least oneinput packet having the compressed headers.
 12. The apparatus accordingto claim 10, wherein the link layer packets including the contextinformation are transmitted through a physical path for signaling.
 13. Amethod for receiving broadcast signals, the method comprising: receivingbroadcast signals including at least one signal frame, the at least onesignal frame including data packets carried by a Data Pipe (DP), and thedata packets including link layer packets in which input packetsincluding Internet Protocol (IP) packets or Transport Stream (TS)packets are encapsulated in a link layer; decapsulating the datapackets; and decapsulating the link layer packet, each header of thelink layer packets including a base header having packet typeinformation and payload configuration information, the packet typeinformation representing a type of the input packets in a payload ofeach link layer packet, the payload configuration informationrepresenting a configuration of the payload of each link layer packet,wherein, for a first link layer packet of the link layer packetsincluding a single packet in a payload of the first link layer packetand an additional header following a base header of the first link layerpacket, payload configuration information of the base header of thefirst link layer packet includes a first value and header modeinformation of the base header of the first link layer packet includes asecond value, for a second link layer packet of the link layer packetsincluding a segmented packet in a payload in the second link layerpacket and an additional header following a base header of the secondlink layer packet, payload configuration information of the base headerof the second link layer packet includes a third value and S/C(segmentation/concatenation) information of the base header of thesecond link layer packet includes a fourth value, for a third link layerpacket of the link layer packets including a concatenated packet in apayload in the third link layer packet and an additional headerfollowing a base header of the third link layer packet, payloadconfiguration information of the base header of the third link layerpacket includes the third value and S/C information of the base headerof the third link layer packet includes a fifth value, and for at leastone of the first link layer packet, the second link layer packet or thethird link layer packet including an optional header following theadditional header of the at least one of the first link layer packet,the second link layer packet or the third link layer packet, a flag ofthe additional header includes a sixth value.
 14. An apparatus forreceiving broadcast signals, the apparatus comprising: a tunerconfigured to receive broadcast signals including at least one signalframe, the at least one signal frame including data packets carried by aData Pipe (DP), and the data packets including link layer packets inwhich input packets including Internet Protocol (IP) packets orTransport Stream (TS) packets are encapsulated in a link layer; adecapsulator configured to decapsulate the data packet; and adecapsulator configured to decapsulate the link layer packets; eachheader of the link layer packets including a base header having packettype information and payload configuration information, the packet typeinformation representing a type of the input packets in a payload ofeach link layer packet, the payload configuration informationrepresenting a configuration of the payload of each link layer packet,wherein, for a first link layer packet of the link layer packetsincluding a single packet in a payload of the first link layer packetand an additional header following a base header of the first link layerpacket, payload configuration information of the base header of thefirst link layer packet includes a first value and header modeinformation of the base header of the first link layer packet includes asecond value, for a second link layer packet of the link layer packetsincluding a segmented packet in a payload in the second link layerpacket and an additional header following a base header of the secondlink layer packet, payload configuration information of the base headerof the second link layer packet includes a third value and S/C(segmentation/concatenation) information of the base header of thesecond link layer packet includes a fourth value, for a third link layerpacket of the link layer packets including a concatenated packet in apayload in the third link layer packet and an additional headerfollowing a base header of the third link layer packet, payloadconfiguration information of the base header of the third link layerpacket includes the third value and S/C information of the base headerof the third link layer packet includes a fifth value, and for at leastone of the first link layer packet, the second link layer packet or thethird link layer packet including an optional header following theadditional header of the at least one of the first link layer packet,the second link layer packet or the third link layer packet, a flag ofthe additional header includes a sixth value.